Mine has to be:
**If you get an "undo" button, it has got to be free. **
Resourceless champions need a short CD skillshot to farm with. is a close competitor though.
This guy was not meant to be a lanebully .... so we will nerf everthing besides his lanebullying
We want to give this champion some counterplay ... so we will gut his numbers till everything counters him
too many champions to list but 
seems to fit here well
My least favorite part of Riots balancing is that they will nerf a champions extraneous power over and over in an attempt to preserve their core gameplay, find out that doesn't work, and then finally nerf the actually problematic part, without undoing any of the previous nerfs, leaving them to be awful. 
Mine would be...
Oh crap, they are all QQ-ing about X, lets nerf everything about them except what is breaking them
bye-bye silence, damage, wave clear, and assassin power!
and then they come back around with this...
Oh, you wanted that nerfed, ok, we'll nerf it! (and leave the other nerfs that pile up to ultimately cripple X champion)
Hey! we finally nerfed his mobility, eh?
rolls by in wheelchair
Mine has to be that you have to be mobile in order to be strong. Personally, I thought mobility was a trade off for something. Guess I was wrong.
point and click is evil
traditional supports aren't allowed to do damage, be relevant or go lane solo. (i hate tank supports)
The fact that they balance "normal" champions in relation to other normal champions, but leave the really extreme outliers alone and untouched.
When a champion is clearly toxic to the game and needs more than a simple numbers nerf, but they find it too hard to decide what to change, so they leave them alone and untouched for years without any changes.
That, once they have settled on a kit for a champion, they will (almost) never change that kit, regardless of how badly-designed it is, or even if it completely contradicts their core design principles.
The thing I hate the most?
That's easy.
Resourceless/Energy champions with any combination of the following: Medium to long range poke Shields Heals
Why? Because this allows them to attrition down opponents with actual resources without having to worry about cost on their end. Champions with these type of abilities tend to be obnoxious as hell to balance properly.
And by the by, while Vlad does in fact have HP costs, his Q fits the above criteria to a T.
Rito's balancing methodology?
I would be lying to say I never get excited about who is gonna be next to receive the clubbing in the face whenever a new patch is released.
And that itself honesty, is pretty sad aye.
But my most hated balancing methodology is definitely their severe lack of communication inside the company where what their right arm does can sometimes just outright contradicts with what its left arm's doing. I won't even try to be satirical and call it my "favourite" since I just absolutely HATE everything about it.
Champions with incredible scaling that are also lane bullies. This has got to be one of the most frustrating things I have ever seen in LoL. To be bullied around by a champion that scales incredibly well into the late game is so disheartening to play against.
For me, if you choose a champion that has an incredible late game, the trade off should be that they are weak early game, or in the very least shouldn't be able to heavily bully people in lane. There needs to be a risk vs. reward. For example, every time I choose Nasus, I'm risking having a horrendous early game for the chance I can stay safe, get stacks, and take it to mid + late game where I can dish out damage.
He is an assassin that excels at extended teamfights. 
Not only does he get to be untargetable, but that is a damage ability. 
AP Fighters are bad (Ekko is an assassin), let's nerf them and completely ignore their just as dangerous AD version. 
"The forums are angry about it, lets nerf it" grinds my gears the most.
Least favorite is "we are going to compensate". Then they don't listen. Ahri players (like myself, mages are not working so she is on the backburner) got a movespeed steroid on our Q and REDUCED acquisition range on our W/R in exchange for losing DFG and losing our charm damage boost. All we wanted was correct targeting, which it did, and a DAMAGE boost on our Q since we farm with it. =/
tl;dr: Compensation buffs are a lie.
Oh and lets not mention Veigar ofc.
When a champion has health costs and those costs might as well not be there for all the shits the champ gives about them.
Or "let's make resourceless champs even better by gutting mana regen for all champs across the board and try to ignore the fact that they already had enough advantages before"
Hm, I would say I dislike it when Riot makes a champion who can max a single ability and get the most damage/waveclear/utility/survivability from that single ability. Fizz is perhaps the worst offender here. Maxxing E gives him waveclear, mobility, survivability, utility, and daamge all at once.
Slightly related: champions who have extream waveclear tied to their primary damage ability. Consider that in S2 Morgana was considered top-tier waveclear, and she had to forego maxxing Q to do that. Now we have the likes of Ziggs/Xerath/Zed/Fizz/Ahri/ect. who max a single ability and get strong waveclear along with high damage output.
Crit.
The amount of risk and reward some abilities get compared to others.
Nidalee can chuck spears that chunk for 1000+ to zero risk of herself. She can miss all her spears and she has no penalty for doing so.
Thresh can miss 100 hooks, but god forbid he lands that ONE hook. It will decide the game. If you think you can punish thresh for missing his hook than hes just gonna flay you and proc his E passive. Chunking you for 200-300 before their ADC even gets involved. In lane that is.
Mine has to be Riot's inaction regarding anti-interactive champion kits. By this I mean champions whose sole purpose is to just stop their opponent from ever being able to do anything or specifically benefit from not interacting.
- Widely known to be horrible to play against, not particularly strong in any areas, never really changed since beta. Runner-up for most anti-interactive champion.
- Possibly the most anti-interactive champion in the entire game, mechanics never changed since release. Ghouls will follow enemy champions a good thousand units without even needing to target them, AoE, healing, etc.
- Her reworked passive is basically "enemies pay more for wards and minions can't see me", she's almost always either brokenly strong or useless.
- He's less egregious than Teemo or Yorick, but his playstyle either revolves around proxying (by definition completely ignoring everyone in the game) or just running around being annoying.
Without an exception it's 
.
Balance wise, she's fine.
Design wise, she has mobility, hard cc, sustain, more sustain, true damage, and on-hit effects. It's just ridiculous.
Changing formally targeted moves to skill shots to "buff" them (we really mean make mobility more powerful).
There shouldn't be any resourceless champions at all. They are always toxic.
There is so many.....
Complex = Better Mobility = better Skillshots are the only means of implementing counter play, so everyone has to have them Nerfing champs based on small sample of lcs games Failing to address item balance BEFORE champ balance on and on and on i could go
%Health damaging abilities...
% max health true damage (i gigl evry tiem)
Build health? % max health
Build Resists? true damage
