I never liked the mutated Rockwell/Monkey Brains design. I always thought it was rather plain. But what I absolutely HATED about it was when he did that stupid popping-out eye thing:
It looks incredibly stupid and it really irritates me.
I didn’t like the designs of most of the in-name-only characters either (like the Neutrinos, Rahzar). And certain redesigns like Casey or Bebop or the Kraang and small things like Don’s gap never clicked with me.
Ones I was surprised that I actually liked we’re Dregg and the Squirrelanoids. Dregg had some pretty cool design elements and could’ve been a really villain in another show (plus I really liked the VA they chose for him). The Squirrelanoid’s designs were obvious homages to the Xenomorphs, so I had to like it.