Guy Gardner by a country mile.
Cookie cutter good guy who worked with special need kids. Gets knocked into a coma trying to help Hal out.
Comes back as kind of a psychopath after Crisis. Became comedy relief/jobber in JLI. Got knocked on the head which caused a personality change so he was super sweet, then back again.
Loses his GL ring in a bet. Gets Sinestro's ring. That gets destroyed. Ted Kord makes him an exosuit.
Gets revealed to be a half alien with Vuldarian powers which cures his brain damage. Becomes a respected member of the hero community and opens a bar for superheroes. Gets killed in OWAW and sent to hell then takes it over and escapes.
Rejects his Vuldarian DNA becomes a Green Lantern again. Saves Oa gets promoted to the GL Honor Guard. Becomes a Red Lantern
,then a Green Lantern again.
*2nd would be Jason Todd.