In the storyline "Hypertension", Superboy met a number of variations of Knockouts during his journey through Hypertime, one of which was an agent of Black Zero, an alternate adult version of Superboy.
Superboy met a number of variations of Knockouts during his journey through Hypertime, one of which was an agent of Black Zero. This was in the storyline "Hypertension". Black Zero was an alternate adult version of Superboy.