Memorial Valley Massacre (1988)
So basically what we have here is Jaws, on a campsite, with a caveman. In other words, a high concept movie. When the writers of this script sold the idea to the producer or whatever, they probably used this exact phrasing to describe it. The poster even rips off the tag line from the Jaws 2 poster!
It takes a little while for the caveman to start killing people. Until then we have to put up with a bunch of awful people:
Bikers: Three bikers and their women, all of whom are totally uncool and past their prime. At one point the head biker is like "I'm just no fit to lead this pack anymore man" and all the rest of the gang gather around him and are like "no, don't say that!" I guess this is the new breed of sensitive biker, the kind that fishes for compliments and enjoys the loving support of his pack.
Awful Family: This family is just nasty all around and it takes way too long for them to die. The kid is this fat manboy who is into petty crime and really enjoys riding his ATV. Cavemen don't like ATVs by the way. They think they are dragons or something.
Teenagers: Two guys and their girlfriend. They are nasty to everyone for no reason and totally out of control! There is a part where they all have a huge party in the rain under a tarp and she just really has to dance! And she does a laughable sexy dance in the rain in her tight T-shirt and oh man the late 80s.
The Couple in the RV: Their plan is to sit in their RV all weekend and watch VHS tapes while drinking whiskey and eating steak. These are my kind of campers.
Love Interest: She's not pure evil like every other character, and only kind of nasty to people being nice to her. So you know she's gonna be okay.
Like most slashers in the 80s, you are watching this to see awful, nasty people getting butchered by a maniac. The characters in this movie are indeed horrible people, but the maniac is pretty lame. He's not even the good kind of caveman (the kind that thaws out after millions of years and looks like a gorilla)! Actually, he's not even a caveman at all! He turns out to just be some kid that got left in the woods and grew up feral and lives in a cave. Hm. So I guess that does technically make him a caveman.
But regardless of his status as a caveman, he just isn't very brutal. Most of the time he just breaks necks. Come on. He does set a bunch of traps all over the place, most of which are awesome spike pits, but nothing like the amazing trap masterpiece in slasher Don't Go in the Woods! However, I wouldn't expect a mere caveman to engineer such a trap, so I'll let it pass.