This one is hard for me. I don't necessarily have a top 10 list, but I will say that the Rat King is probably one of the best villains in the Mirage comics. The introduction to the character in Tales of the TMNT almost made me feel sympathetic toward him (which you could probably tell from my video about it).
But what really solidifies it for me is his appearance in City at War, where Eastman and Laird made the obvious connection to Splinter (because... well, he's a rat). The back-and-forth Splinter and the Rat King had was really compelling — it was as if the two of them were engaged in mental warfare. And the themes of morality, cannibalism, and what makes somebody civilized or not were really interesting. And of course, one of the most compelling parts about the Rat King's appearance is the question of his death. The Rat King had died previously in Tales, and it's not clear if Splinter was merely hallucinating, personifying his own mental debates onto the Rat King, or if he was under a spiritual attack. The story intentionally leaves room for speculation, which is pretty cool.
But at the same time, I'm not really sure how I feel about the whole Pantheon idea from Tales Vol 2. A lot of content from Tales Vol. 2 is pretty hit or miss for me, personally.
My second choice for villains is one that is very underrated: the merpeople. Well, I guess they aren't technically villains in the traditional sense. But I really like their inclusion. It's fascinating to think that there are these strange creatures out there in the world without any real explanation. And I definitely enjoy these kinds of creatures more than the anthropomorphic animal mutants many other iterations include.
