Legions of people entering games to do nothing at all
Every game I've been in for the past several months, there are massive groups of people who just don't want to do anything. They don't play, they don't talk, they don't do anything except sit there gormlessly and wait for the game to end.
I've already been booted down three entire divisions because of these assholes. If you are going to start a game, fucking play it, or don't even log into the client at all. And Riot, you need to seriously start handing out permabans to these lumps, because they are ruining hundreds of thousands of games every day.