I'd like to put this one in the so-bad-it's-good category, but it's simply bad.
We're asked to accept a lot in _Frightmare_: 1. That a group of college students would steal a dead body for fun. 2. Psychics have legitimate powers. 3. An actor who played a vampire, upon returning from the dead, will possess powers unrelated to a vampire (e.g., telekinesis, pyrokinesis).
Let's talk for a moment about the main character, Conrad Radzoff: clearly he is supposed to be a nod to Christopher Lee - and maybe even Bela Lugosi. It's set up early on that he is a killer, but why? He didn't need to be for his ghost to be pissed that college kids took his body. The plot is paper thin here, and I'm not saying it has to be complicated, but at least have some internal logic. I think the writer just heard about people taking Charlie Chaplin, and John Barrymore's corpse - the latter was alluded to - then just ran with it.
Look, this is a bad '80s horror movie that wants to be a slasher, but doesn't have Jason Voorhees, so instead they give you ghost actor.
I can tell the people involved cared about horror, but they didn't have the self awareness to lean into the humor of how bad the plot was or didn't have the writing skills to make this work despite that.
There are two fake outs early on, and I thought they were a hint that the entire story was going to be a movie within a movie. It's not, and I'm unsure if that was a relief or a mistake.