The one thing that sets me off the most.

I can handle a lot of crap in this game. You're being a feeder? Fine, I'll deal with it. Flaming? Whatever, I'll mute you.

There is exactly ONE thing that makes me wish you the worst death imaginable.

"We're not surrendering so you can suffer." This. This is NOT okay. You don't go out of your way to make a game hell for 4, possibly nine other people just for a petty revenge. If you do this, I will report you, leave the thing you said, and let Riot deal with it. Behavior like that is NOT acceptable for a team oriented game. Especially since it will likely ruin the experience for your own team.

Needed to rant about this because this has my blood boiling at this point.