Losing because one of your teammates wants an S as Support
There are a few of those games where you get this guy who plays something like sona, presses w and buys mobis and movement speed to score assists off of healing you while you're at full hp and running at light speed away from every fight, being the only one left alive every time at full hp and mana. Sure you got a 03/15 score, but you legit lost the game because no one can trust you to actually be playing to win. This is the only problem I have with the ranking system for champs.