@Jackone Varying levels of conflicted feelings that you'll be getting from the MC's actions, but there you go.
Feels weird recommending this back-to-back, but
Lost Man has an MC that's doesn't really qualify as a good guy, though he's not bad, and he makes some questionable decisions for his own benefit.
Kasane's MC is also not exactly good, even if we might feel pity or support for her (at one point).
For outright villainy,
End and Save's titular pair are actual, manipulative villains, but it's really fun to follow them.
Now this genre might not be your bread and butter, but
The Villainess Reverses the Hourglass's MC is also a villain that you may or may not cheer for.
Break Blade features the infamous moral grey area, y'know, the war thingy.
Tbh, I haven't finished
Akumetsu, but our protag is a serial killer. Doesn't get more grey than that.
I also didn't finish
Kimi no Knife (more like I'm barely starting to read it) but it fits so there you go.
... Which reminds me of
Munou na Nana, another nice read.
Topping it off with a tamer one in Gorae Byul, admittedly the one that belongs the least on the list but I felt conflicted enough. You know what, nvm.
And it wouldn't be right to not mention
Bokura no Kiseki; that wouldn't be like me.