Well then, Smirnoff.
Uhm, top five most annoying?
Gnar (Ridiculous mobility, especially considering he gets a bonus distance if he leaps off of a target, not to mention haste with attack speed does almost 1k bonus damage on a tank or some other things)
Darius (He's pretty hard to beat in lane and he just smashes the keyboard to win lane half the time, and it's kind of frustrating. Not to mention he doesn't even need his passive to win the lane, but it's just so much worse with it.)
Kalista (Mobility Creep continues on at its fifty mile an hour course. Seriously though, a whatever ranged dash (I think it's like 400-500 when leaping backwards with max tier boots) and unlimited cap on her Rend with a long ranged 100%AD projectile and free wards constantly so your support doesn't need to spend as much gold on wards and neither do you? On top of an aoe 1.5 second knockup, it's just annoying to play against.)
I'd say Zed, but in the silver gold region, besides the fact that the champion in general can 100-0 with no skill required if the enemy doesn't have any mobility, but he's pretty easy to lane against because all Zeds are the same, they just push the lane and then try and poke you and get in close a lot of the time, so you just poke them down every time and use 1/10th of your brain to dodge the skillshots. Still annoying, but managable at my MMR
Lucian (He's just a bitch to deal with still, almost as much as Kalista because he has almost double her damage output early game, not to mention that ALL of his abilities are super easy to land and use, and you don't even need to hit them in order to proc his passive, so he's pretty easy trading, not to mention they can crit. Second most play rate in the entire game because he's so damn easy with so much damage and mobility, it's stupid.)
Ryze (He gets seriously tanky while having a higher damage output, more movement speed then youusually, and snares on top of that. Just not fun to go against, and now he's practically meta top lane.)