The Avengers were a team of superheroes whose roster changed greatly over the years.
United They Stand
A new team of Avengers was reassembled by Ant-Man after the previous team broke up because of Loki’s mischief. This new team was the main characters in The Avengers: United They Stand.
The series featured a team broadly based on the roster for the 1984 Avengers spin-off series The West Coast Avengers, comprised of the Wasp, Wonder Man, Tigra, Hawkeye, Quicksilver and Scarlet Witch(Hawkeye, and Scarlet Witch were also both in the Iron Man animated series as members of Force Works), led by Ant-Man (aka Giant-Man), with the Falcon and the Vision joining in the opening two-parter.
The series featured many of the Avengers' major comic book foes, including Ultron, Kang the Conqueror, Egghead, the Masters of Evil, the Grim Reaper and the Zodiac, as well as associated characters such as the Swordsman, the Circus of Crime, Namor, Attuma, Agatha Harkness and the Salem's Seven. The show made several fan-friendly references to aspects of the characters' comic book history that were otherwise not expanded upon for the uninitiated, such as the Falcon and Captain America's partnership, Hawkeye's partial deafness or Namor's half-breed nature.
Beyond this, however, the series bore little in the way of similarity to the comics, mainly due to its wholesale redesign of the cast, characterized by asymmetrical costume design and the most (in)famous element of the series - Ant-Man, Wasp, Hawkeye and Falcon all wore suits of battle armor, which they donned in sentai-inspired "power-up" sequences.
For undetermined reasons (perhaps due to their rights being tied up in planned movie projects), the Avengers' "Big Three" were not regular fixtures in the series - Captain America and Iron Man made only guest appearances in one episode each, while Thor did not appear outside of the opening titles.