I mean my understanding of these things is that %HP damage is meant to either allow damage dealers to shred tanks, or allow tanks to retan meaningful damage while building primarily defense. But Lee is neither of those. He targets squishies and has plenty of meaningful damage from high AD ratios. So why does he need %HP damage?
Shiyo Kozuki84 votesBecause lee needs to be good in every situation imaginable and always a top tier pick.
Xicashina12 votesHonestly So true, He has 0 counters, and the second he starts being countered by champions he's buffed hard.
AsC4lK51fe8 votesNo counters you say. Must not understand the champion. He needs skill to play and also you can outplay him easily.
Xicashina12 votesOh I have no problems dealing with lee sin, in fact Im quite happy seeing him on the enemy team, as I find him rather easy to deal with. Im saying however that no part of his kit is expressively countered by another champion.
For example, Nidalee is countered by Elise due to her spiderlings blocking spears etc etc. Yi is countered by Lee sin as Lee can out dps him early and snowball off him. In that camp there is no champ who if in the game can make sure that lee can't do anything (not saying you can't shut him down, just saying that he will only be shut down if outplayed I.e. if properly played he should have the advantage in every matchup).
AsC4lK51fe8 votesYeah, I would rather have a champion have no counters but outplayable than to only have counters and not outplayable.
Bârd29 votesWell, not MANY counters.
fuck up his mobility
negates his ultimate
Armor tends to piss him off
People who can quickly and easily CC him (
Stun, 
Silence, 
Fear
Staredown) will leave him a sitting duck halfway through his combo.
Champions with blinks can use them while he does his second Q to take him to a place where he doesn't want to be, and can also use them just before he ults to fuck up his aim.
Doesn't give two shits where Lee kicks him, since he can always go right back to where he was.
Champs like 
can summon units to eat Q's for them.
Can intercept Lee's second Q with body slam.
will crush his dreams of being an assassin.
Also, there is a reason why Riot takes care to keep Lee Sin in a playable state, more so than other champions. Lee Sin is fun to play, leading to him being one of the most popular champions in league. Should Lee become shit tier, that massive chunk of the playerbase (not to mention the pro scene) who main him would cause an uproar. 28% of players plat+ have over 125 games on him, and losing that many players because they left Lee Sin in a state similar to Sejuani, Fiddle (who might be good now, remains to be seen), or Sion would not exactly be good for buisness.
UnderscorBunnies5 votesThe last part caught my attention the most, as something I've always thought, but never brought up here. Lee Sin looks like a really fun champion to play. He's a skill based high mobility champion, and when you play him your success is mostly dependent on your decision making and mechanical skill. That being said, having him deal %Health damage seems a little silly, but the people who claim him to be overpowered is ridiculous.
sp4413 votesI don't think he's overpowered, I just think he's fucking obnoxious. Not only he appears way too fucking often, but he just has so many tools in his arsenal that I never feel like I've got him on the ropes, every time I think I got him, he does something to turn around the fight and wins, or survives.
Ultîma4 votesBeing required to have a particular set of champions on a team in order to deal with a single character is a pretty good indicator that he's broken. Also listing Morgana as someone who can deal with Lee Sin is a bit weird, considering he deals way more than enough damage to disregard Black Shield in its entirety to blow up a priority target.
There's no denying that Lee Sin is fun, but that shouldn't make him trivialize the majority of the jungle champion pool. This blatant favoritism is not doing the game a service.
Spizzle90009 votes"muh skills"
Yosuke Apperu18 votesBecause Riot wants him to fire your tanks at your team like ballistic missiles! :D Well erm.. atleast that's the only reason i could think of.. lol
Zero Skill Tank16 votesBecause for Lee Sin player having Zed-level mobility and burst is not enough and they also need Malphite-level engage by throwing 6000hp mundo in his teams face.
CasterGilgamesh2 voteswhat kinda items does a mundo build to get that amount of health....?
KANYE OBAMA GOD1 votesCinderhulk. The rest is just a normal build. It's easy to get 6k hp on Mundo lol
TotalJerk1 votesYeah, if you're going full HP and ignoring everything else. Which is retarded.
KANYE OBAMA GOD1 votesI didn't say it was a good build. I said it was easy to achieve.
TotalJerk1 votesPoint still stands. If a Mundo is dumb enough to stack that much HP, he has worse problems than a Lee Sin kick.
Uiru15 votesLee Sin doesn't need half the things he has (which gives him just about 2x the number of tools that nearly all other champs have to work with).
He just does, because he's designed to be the best. Which also, conveniently, makes him immune to any real nerfs. And if at any point he isn't the #1 choice, he is buffed. It's sickening.
Ultoblaknite14 votesHis Q has 8% missing health bonus damage, and his ultimate has additional 12/15/18% BONUS health damage scaling.
I do agree that Lee Sin is typically used more or less as a duelist style champion early on in the game, up until about level 11 unless you are way ahead, the missing health Q damage is really good for finishing off low-health targets and increases his capabilities in the jungle as he gains a lot of damage after you smite a camp and then use your second Q active "Resonating Strike" to finish off said camp.
His ultimate having bonus health scaling is a weird concept to me knowing that his most priority targets are usually carries and are squishy, most of which will nearly never build extra health items as a priority short of maybe Rylais, Liandry's, or Rod of Ages on AP mages, or a Black Cleaver, Triforce on AD assassins/fighters that are not tanks. If that is the case, and someone like a Cassioepeia builds a Rylai's and Liandry's, that's 700 bonus health from items, and Lee Sin's ultimate would be doing roughly 120 bonus damage at Rank 3. So I do agree that the ultimate bonus health scaling is a little weird for his main purpose. His ultimate might be helpful for diving tanks 2v1 or for top lane ganks and such, but the scaling doesn't really benefit him anywhere else particularly significantly like you mentioned.
This whole post may seem like a bit of a roundabout essay, but the TL;DR is basically, the Q scaling is really good for him in ganks and in the jungle, and his ult scaling is a little odd, especially with the AD ratios that he already has.
Serevas8 votesTo my knowledge the bonus health scaling was provided when Cinderhulk was out and roaring, so there were a ton of tanks, and massive amounts of HP around, He was supremely outclassed because he couldn't duel the tanks and so for some reason they decided Lee Sin of all champions needed a buff.
But basically my understanding is that they wanted Lee to have a way to deal with league of tanks.
Crett27 votesWell it didn't kill the tanks. It just meant that when he ulted the 7000 HP Sion into the enemy team they all took like 2000 damage
Serevas7 votesThe best way of dealing with a tank is to kill those he's trying to protect, the 7k hp sion doesn't do any damage, so you kill the damage and then work on him.
ModAcademy Kayn13 votesYou haven't seen a 7000 Health damage Sion with a Titantic Hydra then.
TotalJerk1 votesBecause it doesn't exist.
ModAcademy Kayn1 votesYou're telling me, that a champ that can infinitely stack health, through KILLING THINGS, can't reach 7000?
TotalJerk1 votesNot in a game of a realistic length
The Yetii Rider4 votesTo my knowledge the bonus health scaling was provided when Cinderhulk was out and roaring, so there were a ton of tanks, and massive amounts of HP around, He was supremely outclassed because he couldn't duel the tanks and so for some reason they decided Lee Sin of all champions needed a buff.
But basically my understanding is that they wanted Lee to have a way to deal with league of tanks.
No. It was given to him during patch 5.16 in preparation for the League of Legends World Championship. It was to help him deal with juggernauts, not Cinderhulk junglers.
AMYS GRAVE6 votesThe %HP scaling was added to his ult pre worlds season5 well after cinderhulk was nerfed beyond relevance.
EDIT: patch 5.16
Zone of Endless4 votesTo my knowledge the bonus health scaling was provided when Cinderhulk was out and roaring, so there were a ton of tanks, and massive amounts of HP around, He was supremely outclassed because he couldn't duel the tanks and so for some reason they decided Lee Sin of all champions needed a buff.
But basically my understanding is that they wanted Lee to have a way to deal with league of tanks.
It was added to differentiate between the good Lee and the bad Lee Kappa
Also, there's an immediate nerf for Elise on PBE right now
Edit: It was added to help scrub Lee Sin do better and good Lee Sin to do even better
UltraFireFX2 votesOhh noes! Our golden champion can't destroy our golden meta! Lets give him a scaling ratio that not only damages the tank (who also gets deleted from the fight for at least 2 seconds) but deal the same damage to everyone else hit and keep them out of the fight too!
It's almost as sad as killing 
with Tibbers as 
!
AmetDeCrypt1 votesor 
or 
?
Spoofghoul7 votesI think lee should have a 50% chance to kickhimself in the nuts doing 12% max hp bonus damage and applyieng his ult to himself. Because he is blind and has no idea in which direction he is kicking.
GhostOfShrimpmas6 votesHave you ever kicked yourself in the nuts, even with your eyes open? Shit ain't easy.
WiegrafOfValor6 votesI love how lee defenders argue that he's fine because he doesn't have the mobility of a top mobi champ 
combine with the damage of a burst assassin 
with de defense of a tank 
... Guess what kid, neither does the rest of the champion pool.
Lee is disgusting, he has more options than the rest of the champion pool combine, MOBI+DMG+CC and isn't squishy. Sure you're not a tank, you can't jump on the enemy team and sponge the damage, and sure if you build 
you won't be bursting anyone, but that isn't your job.
Lee's job is to disrupt, create picks and engages for the team.. and guess what? he is the best and the safer on the job.. better than any other initiator out there.
: Great initiator, poor escape/engage and rely on his high CD to create a good engage.
: All in with no escape, also rely on CD.
: No escape, rely on CD.
: Rely on his R to initiate, no escape.
: Tanky, Semi-Escape with her dash, but rely on her R to engage.
: Have to walk all the way to initiate and escape, no burst.
: No escape, rely on his Q+Ult or Flash+Ult to create a pick or engage.
Now comes Lee Sin
: **Sustain, 2 engages that can be used to escape, great base damage, absurd scaling, Ult is a disrupt heavy CC NUKE with 600 base damage + %Max HP + 200% scaling. **
Now the cooldowns:
: Engage tool nº1 [Q] - 7 sec // Engage tool nº2 [R] - 60 sec
: Engage tool nº1 [E+Q] - 11 sec // Engage tool nº2 [R] - 90 sec
: Engage tool nº1 [E+Q] - 9 sec // Engage tool nº2 [R] - 60 sec
: Engage tool nº1 [W] - 9 sec // Engage tool nº2 [R] - 120 sec
: Engage tool [R] - 100 sec
: Engage tool nº1 [Q] - 11 sec // Engage tool nº2 [R] - 100 sec
: Engage tool [E] - 6 sec
Engage tool [Q+R] - 110 sec
AMYS GRAVE5 votesbecause % HP is the only way they know to handle champions anymore....
Maximum Morde3 votesBecause they want him to wreck tank junglers during invades.
Knoyle3 votesBecause Tanks need to be as useless as possible. EVERYONE should be able to take down a tank. CC heavy champions? Please, who needs those when you have true damage up the wazoo.
Penta Penguin3 votesI am desensitized to Lee Sin butt-hurt anymore but do you really have to be butt-hurt about arguably one of his better and cooler mechanics?
Kick the huge-ass tank through enemy team, deals more damage because the tank is like a wrecking ball. That is awesome, and nobody else in the game does it. Makes a lot more sense than """""ward hopping"""""
Jungle Lux God3 votesIf I'm not mistaken, it's there such that he can target tanks when you can't target squishies.
While Lee Sin does have the mobility to make sure that this is never the case, what happens when that isn't the case? What if the Lee Sin player physically cannot utilize his incredible mobility to get to the enemy squishies and kick them into your team?
This change allows less skilled Lee Sin players to be able to kick tanks into the enemy squishies' face for engage or kick the enemy tanks away from your squishies' for peel rather than kick the enemy team's squishies to kill them as compensation for not being a good Lee Sin player.
BastionKross1 votesThis is a dangerous way of thinking.
What if you're and you can't get your turrets down? You get your ass kicked.
What if you're 
and can't get your stacks? You get your ass kicked.
What if you're 
and you keep getting kited? You get your ass kicked.
What if you're and you can't target a squishy? You target a tank instead.
You see the difference there? With a lot of champs, if they fail at a key part of their playstyle, they have no plan B. That's what keeps them balanced and gives them counterplay. You kill Donger's turrets, he's much less of a threat. You stop Nasus from farming, you're gonna keep him weak. You kite just about any juggernaut, they're a sad panda. This is true for the vast majority of champs.
Lee just doesn't work that way. He's got the tools to deal with just about anything you throw at him. He's always got a plan B for when you foil plan A. That's why people really don't respond well to his kit; just when you think you've countered him or outplayed him, he's got some way of negating it. If a tank goes in to intercept him from bursting down a squishy, Lee can opt to just ult the tank back into the squishy. And then he ward hops away from any further retaliation, because outplaying Lee is more than a two man job at times.
Anomander3 votesBecause 1 shotting a vayne by kicking mundo into her is funny............
forresto3 votesIt might be to normalize his damage between champs, so he has roughly the same impact on one champ as another.
DunkinNoobs3 votesThe majority of people in this thread (including the OP) don't even understand how the %health damage on Lee's ult even works, and yet they still manage to have an opinion on it. Impressive. It literally only does the %health damage if you kick 1 enemy into another, only does the extra damage to the champion hit by whoever Lee kicked, and the damage scales off the bonus HP of the target Mundo kicked. If Lee kicks a Mundo with 2000 bonus health, any targets Mundo collides with will take an extra 360 damage. Mundo himself will not take this damage.
TL;DR Getting hit by huge flying tanks fucking hurts. How this wasn't in the game ago is a mystery to me.
Fizz Wukong3 votesJust going to leave this here: Lee Sin performs a powerful roundhouse kick launching an enemy champion back, dealing 200/400/600 (+200% bonus Attack Damage) physical damage to the target and any enemies they collide with. Enemies the target collides with are knocked into the air for a short duration. Every time the target collides with an enemy champion, the target also deals 12/15/18% of their bonus health as physical damage.
Read over that a couple more times and reconsider your post.
Mecha MaIphite3 votesLee does not have %HP damage. %bonus HP damage on his R applies to targets he kicked, therefore it is a nuke and not actually %HP damage. His Q second cast is %missing HP and acts like damage amp, not %HP damage.
Earl Eulrich2 votesto promote doing sth. else than insecing the carry? it´s really alright for him to have that, they should rather nerf the basedmg/scalings so he can´t oneshot squishies if he gets ahead.
Sire Hippington2 votesLee was desingned as a jungler back in a time where junglers rarly had the gold to affort damagebuilts, so the %damage was there so he doesn't fall of as hard later on, and also to provide better jungleclears and steals. The damage on the ult is indirect %damage. He does not deal %health damge to the main target, but rather aditional damage based on the targets bonus-health to the other targets it collides with. So it gives him more damage vs squishies if he kicks a tank into their face...
I won't say lee is a great designed champ, but the %damage is wel needed to keep his damage somewhat relevant later on if he doesn't snowball totally out of controll, as he usually doesn't work well with agressive builts if he isn't ahead. His lategame scaleing is still rather bad, and late is there %damage shines the most.
Spacesuit Spiff2 votesThe execute on his q isnt really aimed at tanks, its to let him finish people off without oneshotting soft targets.
His ult is for when you end up kicking the tank instead of the squishy
LaserDeathBlade2 votesLol would you rather he just have a lot more flat dmg on his abilities?
His dmg is split into % dmg so he can be relevant against tanks without exploding squishies
Criomhthann2 votesLee has the kit he does because there is no situation, in Riot's viewpoint, where having Lee Sin as a competitive pick is unhealthy for the game.
