So, name 2 characters whether from the same universe or multiple universes that you know if they were in the same universe they would be rivals or enemies but they would have a one night stand despite that and continue to having that relationship of rivalry.

1) Sombra (Over watch) and Loba (apex)

2)Catwoman (dc comics) and black cat( marvel)

3) Pharah and doomfist (both from overwatch)

4) tenten and Temari (both naruto verse)

5) Hidan and Kurenai (both naruto verse) and yes I know its fucked up but I think its true.

DIO and Eren Jaeger.

Zeke Jaeger and Medusa (Soul Eater)

Armin and L. (fight me I think this is the most plausible one)

Sona (LoL) and Brook (One Piece) - something like the Mozart/Salieri shenanigans.

Taiho (Azur Lane) and Valmet (Jormungand)