Things that deserve to die. Psycho x Assasin/Killer
https://www.mangago.me/read-manga/exotic_love/ (the toxicity just fit them. ruining eachother is their love language)
https://www.mangago.me/read-manga/sun_kindergarten_classmates/ (batshit crazy. i love it)
https://www.mangago.me/read-manga/heavy_boyfriend/ (hidden gem. yandere x yandere ig)
Guilty that I did not reco exotic love but yeah. both are twisted but not in psychotic way.. Just really twisted
for killer x killer:
bloom from mistake (manhua)
mbb (my bad boss)
rengoku-jima
psychopath x psychopath, killer x killer, stalker x stalker, idc whatever it is as long as they're both maniacs