OP champs (there are some not too many, I would say under 10), for example, Fiora who can tower dive spawn turret (1000 dmg a second) with their ultimate, get a kill+ and still live.
People who play OP champs then trash talk about being good.
Many things about the LoL community in general, one thing in particular, random players who play who they feel like, then do horrible at their job as that champ, blame the team, then troll such as refusing to fight, trash talk, and kill steal/attempt kill steals