Purposefully losing ranked games.

We had a draven who got 25 kills and then farmed the jungle and the lanes that weren't pushed at all until the enemy beat us 4v5. What the hell is this? I lose LP for this type of garbage player. He's probably not gonna get any punishment for what he does, I can assume that it's not the first game he's done it. He seems to have done this in other games where he gets ahead and racks up around 450 farm and then proceeds to troll the hell out of the game and lose it on purpose.