Serious and not at all biased list of long overdue nerfs.
Ekko: maybe having an assassin with a 2.25 second AOE stun that can play 3 roles is a little much. At the very least I would expect his W to get limitations against monsters. He's getting away with a 52% winrate with 10% pickrate and 20% banrate since the summer now, and nothing.
Fizz: Don't have much to say aside he's been high win/ban all year and nobody wants to play against this guy (as usual), but unlike a Yasuo, Zed, or Akali he actually performs consistently well and deserves his reputation.
Ashe, Jinx, Jhin, and Miss Fortune: Clumping these ADC's together here, they are pub ADCs to be sure, but across all ranks they are amoung the top picks with the highest winrates in their class by far. Especially Jinx has got away all year being the #1 adc outside of competitive play, and has seen zero changes since her buffs in pre-season 9.
Mordekaiser: He's been way too strong since release. There was a decent nerf that settled him down and gave him worse laning, but the major issue is still with his ultimate; the range is too long and it's just too free to use. A Morde can lose lane but he can always access priority targets no matter what, taxing 1300 gold isn't good enough, at least Malzahar makes himself vulnerable.
Soraka and the abundance of healing: Not merely "a champion" but there's just way too much healing items, healing abilities, and runes that increase healing in the game right now. Add a Soraka into the mix with a fully healstacked champ and 5 ignite with 5 grevious wounds won't be enough. - Her winrate has been super high all season.
Finally we have Diana: actually it's only been 16 days since her mini-rework - still this crap should had been hotfixed 15 days ago. So where's the nerfs for her in Jan 15th patch. Seriously one button pentakill? Revert immediately.

isn't on a nerf list.