Muhammad X

Muhammad X is a fictional character in the DC Comics universe. Real name unrevealed, his first (and so far sole) appearance was in "Superman" v2, #179 (August 2002). He was created by writers Jeph Loeb, Geoff Johns, and penciller Ariel Olivetti.
Fictional character biography.
Muhammad X is the self-proclaimed protector of Harlem NY, using his ability to alter density and gravity to protect the community. When Superman runs into him, Muhammad browbeats him, accusing him of ignoring Harlem and, in essence, the black community. This causes the Man of Steel to question his understanding of race relations and leads to his seeking advice from his supporting cast/colleagues such as Lois Lane and Natasha Irons.
Natasha names a few black superheroes Superman has never heard of, but are apparently well known in the black community, such as Rush & Silence, Stoneyard and Underground. Indeed, the heroes named here have yet to appear in any DC Universe comic.
The issue concludes with Superman confronting X a second time, telling X "...I can't change the color of my skin... what I try to do is something far more difficult... to be a human being. And hopefully, someday, we'll see each other "only" in that way." Superman flies off, to which Muhammad replies to himself "Yeah, well... I guess that's how you sleep at night."