I compared each LoL champion's winrate across Bronze, Silver, Gold, Platinum and Diamond to see which champions perform relatively better at high elo compared to low elo. This list is the 10 that are most improved with more talented players.
#4 - Riven
We've all seen that Bronze Betty who can't E-R-W-aa-Q-aa-Q-aa-Q-aa-R fast combo with animation cancels and loses lane because of it... Tragic really.
Here are Riven's winrates across the board:
Bronze - 44.79
Silver - 47.92
Gold - 49.39
Platinum - 51.68
Diamond - 53.06