Where did the Dark Horse Comics character, Hero Zero, make his first appearance?  I've never seen his origin story.?

Looks like his first appearance was part of the beginning Comic's Greatest World imprint. Basically Dark Horse wanted to launch their own superhero universe to compete with Marvel and DC. So in summer 1991 they announced they'd make 16 issues each introducing a different hero or team, and then most of them would have gotten ongoing series after that. Well it didn't work out since the 16 issues came out 2 full years late, and only a couple of them got ongoing books after, even some announced miniseries were canceled. Anyway Hero Zero was part of those initial 16 issues, and his first appearance was in the Comics Greatest World Vortex #2.