Everything except for Infernal and by extension Pentakill look crappy. Pentakill needs his guitar, and his ult *should* be like a Rock concert, especially with all the Pentakill branding across League. That skin does not do that theme justice. Lord Mordekaiser is pretty awful too, there's no reason why one of his most "expensive" skins should not have different particles.
It just sucks that Morde gets the shaft after the broken promise of adding custom particles after his mini-VGU that put him into his current state of jank, but that never happened. Akali got a bunch of love and care across how many skins, and Morde's four skins can't even get a little love?
Ace of Spades Morde may be a cheap skin, but it should have a golden glow particle similar to how the Arclight line looks. As it is, the dark green energy doesn't look at all appropriate for a skin that is primarily shiny gold.
Whatever, I'm just happy to see my favorite champion dating back to Season 1 get a proper rework. I just wish there was a little more effort put into the skins that I bought with real money in a time before the crafting system existed.