Superman: The Man of Steel #17 [Direct]-Fine (5.5 – 7) 1st Cameo Appearance of Doomsday.

Not even Superman may be able to rescue the orphaned Keith, who's uncovered the amazing secret of the subterranean denizens of Metropolis's underworld. Also: Doomsday is coming...a first glimpse at a new character who will have a chilling effect on the life of Superman! (NOTE: 1st cameo appearance of Doomsday, his gloved fist punching a metal door with a caption that reads '...Doomsday Is Coming!'
Doomsday is an ancient Kryptonian monster, bio-engineered to adapt to his environment and opponent).