Despite appearances, this is a twofold trophy line. Your first step is to complete the storyline of the base Avengers Reassemble storyline, campaign one. Once you have done so, there will be a quest chain around the Scientist Supreme titled Reigning Supreme. It is through doing this quest line that you will get closer to completing this trophy.
Once you have done so, around the seventh step in the overall quest chain, it will ask you to complete the Iconic Avengers quest chain. These involve playing as the base six Avengers and fulfilling their subjects within the Objectives page. For Kamala, Captain America, and Iron Man, you have to simply defeat enemies within certain skill uses or whatnot, while you have an extended chain with Black Widow, Hulk, and Thor. Along with fulfilling their minor objectives, you also have to complete two unique quests for each.
Once you see the Iconic Avengers task within the Reigning Supreme quest line checked off, you will acquire a Ring artifact and this trophy, though there have been some moments where it does not unlock even at this point. If that is the case, it is bugged and I am unfortunately unable to direct you in how to resolve it.