>>107776427>Does Martian Manhunter have any other villains beside him?
Uh. The White Martians, who are like Green Martians but without compassion, decency or kindness - used to be a separate species, then it turned out that the Guardians of the Universe separated the ancestors of Green and White Martians out to curtail their deadly power, but nowadays I think the idea is that there is no innate difference between Green and White Martians; it's just an expression of who you choose to be.
For instance, M'Gann ('Megan') M'Razz, aka Miss Martian, looks like a Supergirl version of J'onn, so to speak, but she was born a White Martian.
Then there's Fernus, the Burning Martian; once upon a time, all Martians were like him, neither green nor white, but reddish and on fire. They are horrible monsters, like Superman with telepathic powers and the ravenous fury of a rabid wolverine, and they have to create gigantic pyres to reproduce (basically, they burn really hot and then split in two).
Anyway, the Guardians of the Universe messed with the Burning Martians so they became the White and Green Martians (I am guessing the divide was unintentional), who are terrified of fire because it's basically their only weakness. Anyway, J'onn trained himself mentally to overcome his fear from fire - because of the connection between the mental and the physical, he reasoned he would lose his vulnerability if he didn't fear fire anymore.
Well, it worked, and he transformed into a Burning Martian. Hurray! It took the entire JLA to defeat Fernus and get J'onn back.
There was, as mentioned, also a vengeful female Martian called Ca'yan, but I have no idea what happened to her.