I read a scanned version of this issue I downloaded with Limewire. It looked like Superboy-Prime's slide into "villainy" came as an accident. From the way I read it, he didn't become a "bad guy" until he popped Pantha's head off by an accidental application of too much force and then followed that up by intentionally killing several others. Before that time he was just having a slugfest with Conner Kent, which is no different than numerous other slugfests we've seen between super-folks. And now his guilt over the blood on his hands will propel him into going even further in his actions rather than admitting he was wrong and turning himself in to face justice.
Having given it a bit of thought, I think it's significant that Superboy-Prime only gained his superpowers suddenly all at once in his late teens and has very little experience with them. Most versions of Superman has him either gradually gaining his powers over several years and learning how to use them one by one and learning the value of restraint (in the case of the Silver Age Superman from a very early age). Superboy-Prime still doesn't know his own strength, and his lack of restraint, combined with his hormonal teenage emotions (especially jealousy, and probably frustration over his not being the hero he saw himself becoming, as well as the disappearance or death during the Crisis of his whole world of Earth-Prime, including his parents and his girlfriend Laurie), is a dangerous combination.
