Source: comicbook.com

Chapter 2: The Avengers

Shortly after that, Iron Man invited Barton to join the Avengers in his place.

Clint agreed, and was placed on the team – which came to be known affectionately as Cap's Kooky Quartet – alongside Captain America, Scarlet Witch, and Quicksilver. The team faced adversity and mockery for not including many of the original Avengers, but Hawkeye added something that no one else before him had: a dissenting opinion.

Now, everyone knows Iron Man as the Avenger who had disagreements with Captain America, but back in the 60s that wasn't the case at all. Hawkeye would constantly play the hothead and fight with his teammates in ways that were new for the Avengers. The Fantastic Four fought all the time; the Avengers, for the most part, did not. But Hawkeye changed everything. He added conflict, and made The Avengers a true Marvel Comic.

And this is the beginning of Hawkeye being great. His solo villain stuff is fine, but it was when he joined The Avengers that he stepped up to the big leagues.