Jadon Voorhees

First appearance: Friday the 13th part 2 (1981)

Jason Voorhees isn't all that happy with what happened to his mom last year and decides to do something about it. What? You thought his mom killed all those teens last year because Jason drowned at Camp Crystal Lake? And that was just some kind of nightmare hallucination where he jumped out of the lake? Also wasn't he a little kid in that jump scare thing at the end of the last movie? Shut up. Jason's a full grown weirdo who's been living in the woods and wears a bag on his head covering up his weird face and wonky eye.

Jason Voorhees

First Appearance: Friday the 13th Part 2 (1981)

The supposed "Drowned as a child" Jason Voorhees isn't happy that a bunch of camp councillors killed his crazy mom and embarks on an epic quest to rid the world of teens who are into sex, drugs, drinking and dancing to terrible music. After hunting down the girl he saw decapitate his mom he realizes it's probably easier to just hang around in the woods near the campground where he "drowned" and his mom was killed, and wait for victims to just come to him.

Yeah I know Jason doesn't get the hockey mask until the 3d-rd movie but I like him better in the mask.
Interesting bit of trivia, Friday the 13th part 6: Jason Lives is the best reviewed of the series and is widely considered the fan favourite even though it performed the worst at the box office and, unlike any other chapter in the franchise, features no on-screen nudity.