A manga where the parents and children are genuinely enemies and try to either put down or straight up kill each other.

I'm feeling morbid today

Bastard (HWANG Youngchan) ?

Kyuuketsuki Maruguritto to Kuenai Gokinjo, it's not evident from the start but the parents are really evil

Hakushaku Cain Series, followed by God Child. You want morbid? You get all kinds of levels of fucked up in this series from start to finish. Now that I think about it, a lot of YUKI Kaori series’ characters have really messed up relationships with their parents. Not allows out right trying to kill each other, but generally hatred towards parents in every series. She’s a wonderful mangaka anyway, so still check her out series out if you haven’t already. 😁