My least favorite ones, in order of how much I dislike them:
Nyx Prime (giant head), the only frame I've bought deluxe for.
Oberon Prime/Valkyr Prime, don't know what their deluxe skins look like, but only because I don't play either of them.
Nidus Prime. (without mutation stacks, he's just a recolor of the base one, and when mutated he's basically just a single color)
Ivara Prime, looks pretty at first, but a nightmare when actually trying to come up with a different color pallete, ended up using her non-prime skin.
OH, forgot.
Voruna - she's probably somewhere betweem Nyx and Oberon in how much I dislike her design. What's with 5 rubber heads?