EVILSPEAK (1982)
Starring Clint Howard and R.G. Armstrong
Howard looks a wee bit too old to play a nerd tormented by bullies at a military academy.
But play it he does—and quite well. The geek gets his revenge on his tormenters by connecting to Satan via a computer and possessing an army of pigs! At one point the pigs terrorize a nude woman in a bathtub. It's all connected to a Satanist who buried some occult artifacts on the school grounds over a hundred years earlieer.
The end of the film is basically a "Carrie" copy, with Howard using occult powers to massacre the other teens.
An average horror film at best, but Howard has followers and many of them are thrilled that this character actor (who had small roles in "Austin Powers" and "Apollo 13") was able to land a lead role.