Champion Mastery
I love the idea behind this, makes it really worth it to start maining a champion and feel very accomplished when reaching level 5 mastery. However, the way you get exp isn't carried out well. You can do poorly on a champ and still get more points because you win. The exp you get should be more based on your KDA, damage dealt, ect. Or if you are a tank, maybe even damage recieved (maybe). Winning or not should be less influential on how much exp you recieve.