I am not talking about who you think is most overpowered. I am talking about which champion do you just despise? For me, it would be 
. I know he is not overpowered, but few things in the game as as annoying as when Mega Gnar pins you to a wall.
Yasuo. Kalista runner up. Champions that don't die when you kill them (Aatrox, Tryndamere) deserve mention as well.
Mine is Lee SIn, not because of moblity, because every time he just walks out of a team fight with a sliver of hp. Not ward jumping, q'ing, or utling he literally just walks out of it and doesn't die.
FUCK YOU SION I HATE YOU I HATE YOU YOU AND YOUR PERMA CC GET AWAY FROM ME!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Totally Blitzcrank.. you can dodge hooks.. but no matter what...You Will Get Hooked. you cant dodge them all.. 9 times out of 10. You lose the game off this. you know its happened to you once or twice.... you get hooked...insta bursted 1v5. then they force a 5v4...win. End the game.. hes not op..but...ITS SO ANNOYING!
Ones with overloaded kits and/or too much safety in their kit.
In Lane: Volibear. You can't burst him down? Too bad,because his health bar doesn't drop past 30%. Passive down? No it isn't. Aatrox. Finally outdueled him? No you didn't. Oh look,he healed it all up. Jungle: Lee Sin. too mobile. Mid: LeBlanc. Can't get close,then she gets too far. Zed also completely controls his lane. Bot: Annie.
because her W makes defensive items useless,
and
because her ult allows her to CC an entire team by pointing and clicking, plus her Q allows her to CC them all again on her way back out... Not to mention that even if her only offensive item is a Black Cleaver, she can burst down an ADC without much trouble.
. If I am facing her in lane, even as one of her counters, I will curse my lot and hope the game will end soon. I cannot enjoy the matchup even if I am 6/0 from outplaying her. If I am mid or jungling, our toplaner will love life because of all the times I gank just to kill Riven. I absolutely loathe that champion, and wish I could turn friendly-fire on when one is on my team.
Probably 
.
I main 
and I know Malz shouldn't really have a hard time against him, but every time I go up against him on Mid I just get this total mental block and just dwell on how I'm about to lose.... 
Yasuo.
Something like vi or irelia or fiora wich will 3v1 with great ezz
Zed, but just because I'm really bad against him.
Fiora easily she has like 100 damage with just a dorans blade
And you cant even hit her in her ultimate she just gets to kill you for free
