Too Much Forfeiting
I'm starting to grow tired of people who simply forfeit a game because they fall behind a few kills. They treat this game like it's Rock-Paper-Scissors and that certain teams will always win, no matter how hard you try. I refuse to forfeit, and I don't stop trying until the game is over.
These people usually beg their team to quit a game only 20 minutes in because they lost 1 tower, or are down 5 kills. When you see people like this, you know they aren't giving their full effort into trying to win because they've already convinced themselves that the game is a loss. Personally, I have come back from huge deficits in score to win a game because people rallied together and worked as a team. However, when you have people who refuse to acknowledge that come-from-behind victories happen, it makes it so much more difficult to pull off.
Honestly, I think there should be a way to track how frequently someone forfeits or initiates a forfeit vote and hand out penalties based on it. If someone is consistently forfeiting or initiating forfeit votes, that's not a play that I or anyone else who cares wants on their team.