I hate how absurdly powerful Martian Manhunter is for absolutely no reason other than he's not human and writers could give him any powers they want by just saying "It's 'cus he's an alien." He's like a 5 year old's wish fulfillment. "I'm a 7 foot muscular alien with advanced intelligence, Superman-level strength, super speed, super stamina, invulnerability, rapid healing, longevity, flight, heat vision, x-ray vision, ice breath, sonic scream, telepathy, psionic blasts, telekinesis, shapeshifting, intangibility, invisibility, and 9 senses."
There's also the implication that ALL martians have the same innate abilities as he does. How were they wiped out?
He should just have telepathy, shapeshifting, intangibility, and flight. He could have a limited form of super-strength and endurance depending on his transformations. He could also perhaps have a form of invisibility, either as a chameleon camouflage-type ability utilizing his shapeshifting, or perhaps as a telepathic trick so others just aren't able to perceive him.
They got wiped out because there was a virus to wipe them out.
Isn't that the new story?
There's also still the problem of how absurdly powerful he is.
It's not much of a problem, really. He still goes up against credible threats that can hurt or kill him, same as any character.