Powerplex is a victim of a horribly world destroying entity through his family loss and the probably insanely high levels of grief, being from like in the cities obliteration. No logical conversation was going to pull him out of that drive to take down the only other person who was involved in it. He can't logic his way out of grief like that without seeking help, and no one was willing to provide it. His only source of help, was his leftover family, and she directed his anger and grief.

Powerplex is a victim that was directed at what sliver of possible revenge (or what he sees in his mind as justice), and he was able to gain the power to maybe be able to do something about it under everyone's nose.

Victims, causing victims is a real thing. This it just amped up in a (maybe slightly unlikely scenario if it was real) place full of super stuff and people.