Asking who the main character is in The Misfits is a lot like asking who the main character of the X-Men is.  You can't really do it, because the X-Men are nothing without the full group, and the stories all focus on the group.  The Misfits is the same way.  There are four people that make up a group, and the story is about their group.  The four members of the group call themselves the Gang of Five even though there are only four members.  It's a sort of inside joke to them; plus they figure that there is likely another social outcast like them that will need to join the group in the future.  

The four members of the gang are Joe, Bobby, Addie, and Skeezie.  In addition to them Mr. Kiley, the school principal, makes frequent appearances as does Mr. Kellerman.  He is Bobby's boss at the tie store.  There are two main characters that function as antagonists to the group.  They are Kevin Hennessey and Dushawn Carter.