No it's not one of the newer champs who have 2 or 3 skins, as those skins could all be considered high quality, rather it's a Champion with 6 skins with one 1 that looks good.
It's Kassadin. Kassadin.
3 recolors of his ANCIENT vectex looking base model, of which 2 are legacy (and nobody misses except as a Christmas meme), 1 which costs 975 even though it's just a recolour.
The other one, Pre-void, being barely more than a recolor and is at least "something", not to say it's interesting. All of the splash arts are ancient as hell, before 2011, and haven't been updated unlike his Base Skin. Not that they'd be helped with new splashes, the skins are boring in game.
His only good skin, being nearly 4 years old, is Cosmic Reaver Kassadin. Of course Cosmic Reaver Kassadin is good; but that's all Kassadin has, it's the only quality skin he has.
Taliyah, Kled, and Ivern may only have 3 skins, Ornn may only have 2. But even at their worst, their quality is somewhere above awful.
But Kassadin who is 10 years old and has maintained a decent playrate, has only been thrown one skin in the last 8 years.