Sauron (Marvel comics).

Stegron is, somehow, a whole other (yet remarkably similar) character, with practically the same goals, so it's easy to confuse them.

(Frankly, sounds like Len Wein and Gil Kane might have forgotten Sauron existed and independently reinvented him, from how similar they are; there must've been something about turning people into dinosaurs in the early Marvel zeitgeist, I suppose, since they're both quite ancient characters, Sauron having been created in 1969 and Stegron in 1974...)