I think it was a one shot? The MC was female, I'm pretty sure. Might've been violent fantasies, but I'm almost certain they were intrusive thoughts.

I remember distinctly the way the artist illustrated them: one panel everything would be normal, the next everything would get kinda bloody, and after that, back to normal.

Honestly, I don't really remember the plot, but the way her thoughts were conveyed stuck with me.

Also, I wouldn't mind looking through something else where the MC has similar intrusive thoughts? Doesn't have to be this specific one shot that I can't quite remember.

Not sure about the one-shot but Konya wa Tsuki ga Kirei Desu ga, Toriaezu Shine has a male MC that is kind of like that.

Thank you, I'll take a look at that!