Eh, theres a couple of factors in play here:
-Sparks got this personality via crossing their mean streak with the Wizardmon's high intelligence and secretive nature. This meant that he was thoroughly avoiding corrective behaviors AND playing down the Dark Manipulator angle of Vamdemon. Worse, as Wizardmon tend to have confidence issues, he gets more sadistic under stress to hide his unease.
--As FlaWizardmon he'd still be mean, but he'd be more like...Witchmon Ardat about it. Instead of jerking people around him like puppets on a string to feel in control, go to Enuff Dakka.
-Vamdemon don't have friends. They have minions. We've been eroding that, but its not enough. He needs an actual social group, and Pit is...is anything halping.
-FlaWizardmon has its own evolutionary vents for it, which are likely to deflect away from Vamdemon's extreme more easily:
--Sparks has enough melee stats to make Mistymon work, especially as a FlaWizardmon(which is melee-y), but he lacks honor to be a Knight. He's not opposed however, lots of cruel knights out there.
--WaruMonzaemon, well, it'd take FlaWizardmon's fighting spirit being broken. Kind of a Dark Evolution there.
--Wisemon is not a nice mon. But it works for Sparks as is, he mostly lacks enough stats and magic to get there. FlaWizardmon gives the room to get there.