DO NOT KILL THE MARTIAN MANHUNTER!
The Manhunter from Mars, J'Onn J'Onzz, has always been one of my favorite characters despite periodic exiles imposed by the editors at DC Comics.
Although reminiscent in some fashion to the Last Son of Krypton given their shared status as male survivors of a lost extraterrestrial civilization who immigrated to Earth and joined the Justice League of America, the Martian Manhunter is more alien than Superman yet paradoxically is more "everyman" in the sense that his shapeshifting abilities allow him to physically resemble anyone or anything else he can imagine. He is a more tortured being (than Kal-El) who as an adult on Mars had a wife and offspring and other family members whom he remembers yet he transcends, in part, his profound existential alienation through a commitment to justice for the innocent from the street level to the cosmic, bonding with other adventurers, heroes, and law enforcement in this knightly enterprise.
He is a well-rounded, three-dimensional being, who broods and philosophizes and ponders the meaning of this life but yearns for junk food. His short-lived series in the Silver and Modern Ages were intriguing, showing the complexity of this powerhouse detective, combining Bruce Wayne and Clark Kent, and his telepathic abilities made him the closest DC equivalent to Marvel's Professor X (excluding Saturn Girl of the Legion of Super-Heroes). If anything the Martian Manhunter, a functionally immortal character, ought to be far more visible in the DC Universe than he has been so rather than "killing him off" for cheap thrills, ratings, and sales, make this wise, mind-reading, polylingual shapeshifter more integral, advising the JLA, the Teen Titans, the Outsiders, the Doom Patrol, Checkmate, the Suicide Squad, the Omega Men and individual heroes.
Give him more limited series. Team him up with more heroes. Expand his rogues gallery. Allow him to time-travel and meet up with the Legion and the Wanderers. Put him in the Brave and the Bold.
Truly, the Martian Manhunter is one of the most distinctive change agents in comics history.
Let him live!