Eternals' Gilgamesh had the worst Avengers costume in history. Joining an unusual team roster in Avengers 300, Gilgamesh's Avengers costume breaks every unofficial rule of superhero design, dressing him in villainous colors and a scaly, bull-head helmet.
Gilgamesh is one of the strongest heroes in the Marvel Universe, but in the attempt to give the Eternal an equally powerful costume when he joined the Avengers, the publisher completely failed. Gilgamesh might have one of the coolest costumes in comics now, but in the '80s, The Forgotten One was given a rebrand that led to one of the worst costumes ever made. The look turned the menacing hero into a laughing stock.
Gilgamesh, aka The Forgotten One, is one of the original Eternals from Jack Kirby's initial run on the cosmic heroes. Like his fellow Eternals, Gilgamesh is effectively immortal. The Forgotten One is the group's powerhouse and is often considered the strongest Eternal in terms of pure strength. The character was adapted to live-action in the recent Marvel Cinematic Universe film, Eternals, where he was played by actor Don Lee.
It's rare that a costume can have so many different colors and details and still be absolutely horrible - as Gilgamesh's Avengers ensemble is among the worst costumes in Marvel history. Alongside his fellow Avengers, he looked like a joke. Thankfully, Marvel wouldn't keep The Forgotten One's look long as he would later be injured in battle and return to the Eternals.
Would Gilgamesh have lasted longer on the Avengers and be remembered more fondly if his costume hadn't been the monstrosity it was with the supersteam? It's hard to say. But, it's also hard to deny that Gilgamesh's costume with the Avengers was one of the worst costumes, if not the worst costume, ever worn by a member of the team. Thankfully, Marvel Comics quickly ditched the look. .