Thantos, The 3-In-1 Man
Nemesis: Martian Manhunter
Other Major Foes: Zook
Appearances: One comic story
Powers: Super-strength, nigh-invulnerability, flight, super-spinning drill head, self-triplication, vanishing, and height alteration (growing & shrinking.)
Bio: Thantos is an other-dimensional thief seeking to find the necessary means to stay on Earth permanently for his evil ends.
Win: The Cosmic Creature (6-3); D'Kay D'Razz (9-5); Ryx (4-3*); Triumph (?)
Lose: Gorilla Grodd (6-4*); The Lizard Men (?)
*Stats reflect the point value of matches with 3+ participants, not direct confrontations.
Other Major Foes: Aquaman Family
Appearances: 6 comics.
Powers: Amphibious, enhanced senses, superhuman strength/speed, mind control, and illusion projection.
Bio: Thanatos was a being trapped in the other-dimensional "Netherspace" by powerful entities called "The Others" until he could prove himself evil enough to be returned to plague reality. Thanatos could temporarily access Earth when victims gazed into a magical mirror that mesmerized them. Thanatos could then assume their form and walk the Earth for a time, committing evil acts. Upon encountering Aquaman, Thanatos chose him as the template for a permanent form. When Aquaman's wife was in the grip of madness after the death of her first son, Mera was lured into the Netherspace, where she gave birth to a second ill-fated child. Aquaman eventually ended up in Netherspace himself for a time, and while imprisoned there Thanatos was freed and assumed Aquaman's identity. Shortly after declaring war on the surface world, Thanatos was murdered by Major Disaster, who had been contracted to assassinate Aquaman.
Here's something we haven't seen much of so far-- a Martian Manhunter foe who really is quite similar to a better known rogue from another hero's gallery, but the Vile Menagerie member is the older, more powerful, and less derivative of the two. If only Thantos had made a few more appearances, or had any commercial value, this really would have been the complete opposite of the norm around here. Of course, I did have to go fishing into Aquaman villains, which is a notoriously shallow pool to draw from. I can't believe Peter David not only killed this guy early in his run, but did so in such an arbitrary and frankly stupid fashion. Anyway, while I think Thanatos would hold up for a while, especially in Netherspace, the 3-In-1 Man simply bowls his over with superior abilities and a lack of compunction in using them. Hell, I think Thantos might even like Netherspace, and would certainly use it as a stepping stone to Earth.