An overview on the "broken champions" timeline of League
Wayyyy back to the juggernaut era:
Going back to the tank assassin fling in league it was:
-> 
-> 
or 
The Time of the Mages (mage reworks):
Then we all know the Zed stage where every Zed sympathizer was crucified
And now it appears we are into the Voli with his side-kick Vlad:
or 
The Consistents:
(although the anti-ahri movement hasn't been active recently)
We must not forget:
The Age of Xin Zhao
The Age of Lucian
The Age of (AP) Ezreal
The Age of (Blue Build) Ezreal
Mundo's Time of Dominance (my personal favorite period of League...fond memories)
Quinn's Top-Lane Throne
The Meta-Reliant Riven
Now I'm positive that this post will be bombarded by downvotes because of differing opinions, and I'm ok with that. But I post this based on my experience and it seems like there will always be a "broken champion" in the game and when they are nerfed slightly a new "broken champion" will be discovered despite not being changed at all since the time of the last broken champ. Obviously some differ in how good they are as the meta changes, but sometimes a champion just simply doesn't change to take the previous broken champ's throne.
Maybe...just maybe...a champion is broken because of our gameplay as we adjust to different metas? I mean sure, sometimes there are some champions that are outliers in terms of performance where they do exceptionally well, but in the future maybe evaluate yourself and what you could've done better instead of the classic "omg this champ is too op plz nerf Rito".
The point is, there will always be a "broken" champion or class as is the nature of Mobas. Riot's goal is not to balanced the game 100% because that leaves no room for improvement and creates a stale game, their goal is to rotate metas and preferable picks constantly to shake it up and create a live and adjustable game. It's what keeps the community entertained.
Feel free to point out any stages or specific champions that I missed (I'll definitely add them to the list if I feel it fits). I didn't feel like going back any further than the tank fighter/assassin meta because I just woke up but feel free to suggest earlier stages of "brokeness" as well, I had a lot of fun going back down memory-lane and looking at the different eras of outliers as I've played through league.
