Mississippienne and I both vote for the Saint of Killers from the Preacher series.
This guy killed Satan, The Angel of Death, and even God Almighty Himself with a single shot from one of his Walker Colt revolvers.
A line of American tanks firing everything they had couldn’t even slow him down. A friggin’ nuke didn’t even render him a scratch. He was, however, still subject to the Word of God via Jesse Custer.
To whom would you give the title, “Most Powerful Fictional Character Ever”?