My Hero Academia AU where Rei is part of the League of Villains:
Escaped Fujiya shortly after Touya's 'death.' (Or discharged herself and didn't go home.)
Laid low for years until recruited by Kurogiri.
Efficient assassin of the group yet unintentionally became the 'cold-hearted' Squad Mom (Meticulously making sure everyone else has enough food/water, wears their hats and mittens when the weather's cold, hyper-alert to when someone starts getting sick/injured, everyone is too afraid of her to argue.)
She recognizes Dabi, he recognizes her, they're playing a game of chicken in who directly calls out the other first.
She doesn't say much, so everyone else is debating what beef this middle-aged former housewife can possibly have with society.
Cannot be identified by heroes since ice-based Quirks are common.
Always keeps her face hidden when heroes are present.
Kinda just want to see her mop the floor with Geten and after a brutal defeat, just coldly whisper, "Amateur."
'Dabi's Dance' (Rei’s Dance?) would be interesting because realizing your dead child is back from the grave is a moment of shock and horror, but realizing you've been fighting the mother of your children this whole time is bonafide WTF moment.
Honestly, though, I picture it looking less like an unhinged speech and more like this:
