He was originally a one-shot silver age villain who was created by Zemo to join the Avengers and betray them. Of course he had a change of heart and died heroically instead. Then he stayed dead for about a decade until an incident where allegedly Stan was so annoyed that DC had created a character called Power Girl after Marvel had released Power Man (Luke Cage) that he ordered the Avengers writers to bring Wonder Man back (cuz Dc has Wonder Woman). Whatever the case, he got resurrected in an extremely contrived and shitty storyline and then just sort of hung around doing not much other than be insanely OP and make a lot of the Avengers feel useless. He was kinda fun as Beast's straight man but other than that they really struggled to find a role for him. They tried a bunch of weird things with him, the most famous of which was making him a movie star. He was also on the Avengers West Coast for a long time as their muscle, but got killed off again at the start of the 90s because I don't think anyone really knew what to do with him.
Then Kurt Busiek brought him back in Heroes Reborn and admittedly did a pretty decent story arc with him, but there was literally no reason for him to stick around after that.