@Orenoname: According to this manga, you need to be a muscle-headed sentai leader fighting against a villainous organization that includes at least one female leader who is not only gorgeous but is secretly a good girl.
@Purplelibraryguy: I thought of it, but that most likely will lead the defectors' original faction to ramp up their aggression in a misguided effort to liberate their ex-comrade from the "obvious" mind-control / deception/ blackmail that they're being subjected to. Also, in Desumi's case, she might have a compelling reason for being a "villainess" that makes it unthinkable for her to defect to the sentai side.