As title says. I only started playing since Rek'Sai release, and the two I can think of is release Camille and one patch where Xin Zhao would heal insane amounts ridiculously fast.
Eve was both. At first she was utterly useless to joke character status. Then they reworked her, and she could 100-0 your whole team while remaining intargetable.
Xin release he was OP Tryndamere constantly on ult was OP Syndra was hot garbage at release
Also fizz troll pole was legitimately broken at release. 1-5 seconds of untargetablility
you should have seen the outcry and hatred for CertainlyT
and 
were really OP.
Syndra was garbage.
Ezreal is pretty OP. That man can do anything. Mhmmm :)
Lux was pretty bad on release. They had to redo her splash art to incorporate make up because she was so ugly and her neck was weird.
Zyra rivals Xin when it comes to OPness upon release. Zyra was hotfixed nerfs to help tone her down
Yorick was considered bad upon release, as was Riven. I think they both got hotfixed buffs (Riven definitely, can't remember with Yorick).
