So... when you have a troll
What do you do? Please don't say, "Mute them. Focus on doing your best." That honestly isn't a plausible situation. It's not like it prevents them from feeding, or MIAing from teamfights. It's not like it forces them to call MIA, push turrets, or farm minions. No, honestly... it does the opposite. When someone realizes you muted them, they try even HARDER to troll you.
Secondly, don't say that it will "balance out." That is the biggest load of crock I have ever heard about League of Legends. That's what I was told in season 2, and it still has yet to balance itself out. Out of my last ten games that I played ranked, I had one game with a serious team. That means 9 games with trolls. I suppose to clarify when I say troll, it isn't always someone intentionally feeding. It could be someone refusing to team fight. Or an ADC who targets the tank every team fight despite being asked not to multiple times. Or an ADC who doesn't even fight with the team but rushes in after you all 4 are dead and then dies anyway. Or an ADC that has like the longest base range in the game and decides to farm minions instead of killing the 3 melee champs coming at her who are all literally under 50 hp. Or the jungler who comes to gank by strolling down lane from the base, therefore losing any element of surprise and then only robbing farm and leeching xp before leaving you a level and a half behind and down the 24 farm they grabbed while "helping" your lane. Or the jungler who ganks so much he is level 4 when everyone else is level 7 but he still dives under turrets anyway. Or the AP champs buying Avarice blade for the "gold."
Long story short, I get a lot of trolls. Sometimes, I try to ignore them and play anyway. Sometimes I just say fuck it and start feeding like they do. Because really, there is no point in trying to carry someone who is trying to lose. It's like jumping in a river to save someone who is drowning only to have them thrash around so much that you drown too.