"God you suck!" "You're terrible, uninstall!" "U r so bad." "Report this trash."
Stops playing
"Wow you're so toxic." "Wow can you not throw pls?" "Report for inting."
What goes around comes around. If you harass someone and they stop giving a damn, don't point fingers. xD
I'd say mute and move on. You aren't doing yourself any favors by not playing the game (actually an argument could be made that not playing LOL is much better for you), at least there's a chance for you to win if you keep playing.
I agree with OP. If people start trash talking on my team, I just farm till we lose, basically I throw without feeding. Then I report immediately after. And often I get the popup that someone got punished if they spewed a string of crap like that. The new meta is play to get teammates banned, not play to win.
[slayer-jinx-wink]
