Sorry for the double post, but another idea:
Nightwing raids a Lexcorp installation. Doesn't do enough damage to hindr Lex too bad, but Lex is annoyed at the former boy wonder for sticking his nose in Lex's business and decides to take out his frustrations with Nightwing on his harem.
Specifically, he brings in Batgirl and Starfire. They're not interested in each other like Babs and Kara, or Star and Raven, so he has to doll mode them, and then has a debcacherous threesome with the two redhead lovers of Dick.
Could also unlock their mind but keep body control, and tell them that Dick has been playing them off against each other, for whenever Dick's in Gotham he's hooking up with Batgirl, and when he's with the Titans he's fucking Starfire. Just to create jealousy and resentment in them both while they're forced to 69.
This could also be used for other hero love triangle situations, but I think it may be most toxic with these two