Runes Reforged Kill League
I don't remember what season they did it, I know it's a quick Google search, but I know there were not near as many complaints about balance.
No lie, the 6% passive spellvamp with WotA broke champions like Morgana & Vlad.
Malphite & Rammus with a full page of armor runes was absolute hell.
Outside of those few abusive examples, game was better. Keystones and Runes Reforged ruined my favorite game.