homunculus is definitely a must read in this genre. battle royale, berserk, misu misou, n i cant remember any others but if u like horror u might wanna check out some visual novels/eroges cuz some of those r super frightening lol.
I don't know if these are considered horror (Gory mangas) but here's my recommendations: The promised neverland, berserk, tokyo ghoul, chainsaw man, Uzumaki, Juujika no Rokunin, The Horizon (This 1's actually a manhwa but the vibes and plot are immaculate), and Hell's Paradise
