Hannibal lecter and true crime make serial killers look like supervillains but really they're just Steven Miller if he was broke.

Until the combat vet gets triggered by his PTSD, but then we already have Rambo.

There was one fan fiction where the A-Team was abducted by aliens. Let's say they promptly broke out of confinement, locked themselves in a room with a bunch of alien goodies and went underground in a nebula. That was a fun one.

Instead of a serial killer, maybe an obsessive weirdo who can figure out how anything works (and how they can be made to not work) and really, really wants to go home.

The aliens keep trying to find their captive, but parts of the ship keep breaking.

What about a serial killer that normally targets combat vets??

Have you seen Predators? This is directly addressed in that movie.

Okay, so the aliens don't abduct him. They pose as humans, ala They Live or Men In Black. They don't know he knows they're aliens. They're his family, friends, and business partners.

Why not both? Ever watch criminals minds it's always "ex military"

Osiris with Linda Hamilton.

And most combat vets are retired mercenary serial killers.