Don’t know anything about this movie, just seen few scenes from it on some “Top 10 Hidden Gem Slashers” video ages ago.
The only thing I barely remember from the plot summary is that it was about an American soldier who died in war and then later came back from the dead and murdered his girlfriend because she cheated on him while he was gone.
That plot has some similarities to Deathdream [AKA Dead of Night] (1974). https://en.wikipedia.org/wiki/Deathdream
Sound like
https://en.m.wikipedia.org/wiki/The_Prowler_(1981_film)#Critical_response
That’s the one I was looking for! Thank you very much
Solved! Thanks Will!