If Cait can't abuse Runaans, why can Twitch?

What happens is that Runaans shots deal 120% DMG to the first guy and 100% to the next guy it hits.

You said it backwards in your first post.

But no, you are absolutely wrong about this being abuse. Runaan's Hurricane is intended to deal 40% damage to a nearby target, and Twitch's ult is intended to deal 80% damage to a target behind him. Overall, Twitch is getting exactly the intended amount of extra damage from these combined bonuses.

Base auto attack 100% damage + 80% + 60% etc. from penetration + 40% x 2 from Hurricane bolts.

There is nothing here dealing damage in a way that it isn't intended to. Twitch is not getting anything special from Hurricane other than the intended two 40% damage bolts.

If there's a problem here it's that Twitch's ult + Hurricane is dealing its intended damage in an unintuitive way, not that it's dealing unintended amounts of damage.

Caitlyn was an abuse case because on top of getting the standard collateral damage bonus for building Runaan's, she also got a disproportionately large single-target DPS increase, which outperformed intended single-target DPS items and was not an intentional function of the item.

Twitch is a notable user of Runaan's Hurricane because he is able to apply it on top of his innate collateral damage. He's an above-average user of Hurricane for sure, because it builds onto his core strengths, and Hurricane's on-hit interactions synergize well with BorK and his passive + E. These are intentional, straightforward bonuses, and they cater to the type of champion Twitch is and the type of effect Runaan's is supposed to have on a champion's damage output.

Twitch being too strong and Twitch abusing Runaan's Hurricane are separate discussions.

wrong: Kalista, Kayle, Teemo, Kennen, Kog'maw, Tf, Twitch, Ashe and Varus were all Hurricane users. Some on special itembuilds, some built it (and still build it) all the time (looking especialy at Kalista and Kog'maw). Only Caitlyn, Jinx, Tristana, Kindred and Xayah came to building Runaans after it got Crit (or the champs were released ;) with some of the listed champions above now buying it maybe more often as before. Look how Runaans works on Twitch, Jinx, and Kayle. Look how Runanns works on Ashe, Varus, Kog'maw, Teemo, NOW on Cait and Kennen. And look how it used to work on Cait, Kennen and i believe is still working on tf:

The 3rst three get from the purchase of this aoeitem just more aoe. Funny how Twitch, maybe with the highest Range, ahs the least benefit of extra Damage on Primary target. Cause the Bolts on the secondary targets don't pierce threw enemies. But Jinx does triple aoedmg, so damaging a primary target gives them aoedmg from the secodnary targets as well and secondary targets get runans damage and the aoe from the main target. I believe on kayle its like it is on Jinx. Point here is: If these 3 fight 1v1 with no other enemy champions or Minions, Runans provides no strenghts compared to the other Zealitems beside that it has higher Movementspeed and higher Attackspeed as Stattiks and Rapidfire. But these 2 give you extra Damage regardless if it is a 1v1 or Teamfight. And Phantomdancer gives you more Attackspeed, more Movementspeed with enemies near you and Dmg Reduc vs the last enemy champion hit, making it still the best 1v1 item. On the other Hand Jinx aoe rockets are slow and cost mana and Kayle and Twitch have limited Time on their natural aoe.

The secodary Category doesn't have aoe basicattacks and get definetly not increased damage on a Primary Target if there are multiple targets. Still they share their onhitdmg, if it is Ashes Slow and Q Damage, magic onhit damage or increased Headshotdamage. Keep in midn that even if Caitlyn doesn't get stacks anymore threw runans, her headshotdamage is still applied to secodnary targets.

Now the last category was mostly removed cause Runans, the Aoe Damageitem, increased their effectivness on Singletargets heavily too. Caitlyn and Kennen got stacks faster. Faster Stacks meant for Caitlyn more Damage to a primary target, far far more Damage as Jinx can provide with Aoe Rockets. And Kennen could place his Marks much faster, so even in Solotoplane with Minions it was a big diffrence if he was alone or before buying runans or if he had Minions. Both were obnoxius. To compare that, imagine if Ashe would get her q not after 4 Autoattacks but after 2 with Runans (she can appliy the damage to mulitple enemies saiying it again but not get stacks threw them). Or if Fervor would work like that, geting with Runans it triple it faster. If i read it correctly on lolwiki Tf still has this interaction, but hell: He probably still has that cause no one realy plays ad tf cause it sucks.

Conclusion: It is fine, if Runans helps Champions to deal more aoedamage and increase champions effectivness a bit. But its not fine that it doubles or triples a champions effectivness. Twitchs interaction isn't even that big. You don' rush this item on Twitch always cause stattiks is atm the most effective zealitem and sometimes you not even buy it. But have fun playing Kog'maw, Kalista or Kayle without Runans. Kalsita is special that she depends far more on her e damage as Twitch or Xayah and she cang et a reset after she kilsl one target with it. So its a singletarget damage increase but only after she kills one singletarget before (like tristana passive e).

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There are stronger on-hit users than Twitch that benefit from this without breaking the game, so it still stands that Twitch's passive should not be exempt from a commonplace Runaan's Hurricane interaction.

Caitlyn was an abuse case because on top of getting the standard collateral damage bonus for building Runaan's, she also got a disproportionately large single-target DPS increase, which outperformed intended single-target DPS items and was not an intentional function of the item.

His passive isn't the issue, its his ult. He melts people since when he ults he shoots 3 ult bolts at a time, which is insanely broken. Yes I understand its an auto attack enhancement, but its busted and stats show. Why is he allowed to shoot 3 PIERCING LONG RANGE autos?

Just imagine if Jinx or Ashe were allowed to shoot 3 rockets or arrows due to it? It isn't far off.

If his ult didn't work with Hurricane it would be 100% fine. Until then he is one of the most busted ADCs until Riot changes it to being letality crap again.