Especially in low elo, trolls are rampant. I've had 4 out of my last 6 games ruined by int feeders running it down mid. And people that LITERALLY join champ select, openly say theyre gonna troll, steal your role, switch to smite last second after you decide to just take their role and be the good guy, and then flame you all game for playing a sona top with support item. This shit isn't ok, Riot needs to crack down on these people. You can just look at their profiles and see they troll in every ranked game, so why is it allowed to continue? Is it because they can potentially buy skins and riot desperately needs the money? Come on Riot, get your shit together.
Edit: Hell, the ones that run it down aren't even that bad, since they're worth less than a cannon and give bounties that can get you fed and back into the game if you play well. It's the ones that do everything possible to ruin your game except openly feed that make this game not worth playing to me.