My ally told the enemy team in all chat where I was so they would come to kill me. It doesn't get any more toxic than this, but how do you even report that? I'm sure nothing will happen to this toxic piece of trash because Riot only likes to ban good players and people who stand up to bullies while protecting game destroyers like that.
The same fucking game I have another ally who just goes around the map trying to last hit monsters and minions that you are killing to steal them. That's all he did the whole game. He stood there watching the enemy team kill me, never tried to help once. But he was always there to try and take the cannon minions or buffs.
Riot's report system is working perfectly.