After being killed off in Friday the 13th: The Final Chapter, original Friday the 13th film, Jason claimed a pile of victims over the course of those three sequels.
At the end of The Final Chapter, Jason gets hacked to death by Tommy Jarvis (Corey Feldman), who would become his nemesis for a few movies. It looked like Jason had returned in Friday the 13th Part 5: A New Beginning, but that turned out to be a copycat killer using the Jason legend to hide his identity. After that film tanked at the box office, Paramount producers wanted the real Jason brought back.
Since Jason had been pretty definitively killed in The Final Chapter, it was up to writer/director Tom McLoughlin to figure out a way of resurrecting Jason from the dead in Friday the 13th Part 6: Jason Lives that wouldn't cause too many fans' eyes to roll back into their heads. While not perfect, he did the best he could.
Friday the 13th Part 6: Jason Lives Resurrects Jason as a Zombie
Friday the 13th Part 6 sees Tommy Jarvis once again return, this time played by Tommy would turn evil is abandoned, but Tommy is still damaged by his encounter with Jason. In an effort to make sure Jason was in fact dead, Tommy and his friend Allen head to Crystal Lake cemetery to dig up his grave. Then, upon finding Jason's rotting corpse, Tommy commits an act of epic idiocy by attacking and stabbing the body with a metal fence post. Lightning then strikes the post, reviving Jason as a nearly unstoppable zombie.
Friday the 13th Part 6: Jason's Resurrection Is a Nod to Frankenstein
The method used to revive Jason in Friday the 13th Part 6: Jason Lives is obviously a nod to Universal's 1931 horror classic Friday the 13th Part 8: Jason Takes Manhattan, but that's a story for another time.
