So, I was with an Ezreal, and I was running away in lane when he was fighting because if I tried to help, both of us would've died. He said I sucked, and I said no I don't, you're 0 and 2.
So then he started to argue alot, like ALOT. When the game ended he was lvl 12 because he sat at base complaining about how I "wasn't supporting the team" And nonsense like that. Here's some pics.

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Report in game, use the tribunal. It's against summoner's code to call people out on the forums by name/ss.