Skeletor

So one of my favorite villains from my childhood is MonStar from Silver Hawks.  And of course there's Mumm-Ra from ThunderCats.  But here you have probably the most awesome of them all, who doesn't transform into a more powerful entity, unlike the previous two; Skeletor.
 I was a big fan of He-Man and the Masters of the Universe as a young child.  I had all the toys.  Seriously, I had over 300 different Masters of the Universe dolls. I had a relative who worked at Toys R' Us heh. It was great.  Oh, btw, I call "action figures" dolls.  So, yeah.