Here are some potential contenders, depending on how you define "Ultimate Superman" and the rules of the fight:
Within the Ultimate Universe:
* The Authority: This group, particularly individuals like the Engineer and Apollo, could pose a significant threat due to their advanced technology and cosmic powers.
* The Ultimates: Depending on the version, heroes like Captain America, Thor, and Iron Man could potentially stand a chance with strategic planning and powerful weaponry.
* Other powerful beings: Depending on the specific event, other beings with strong abilities like the Hulk, Doctor Doom, or Galactus might be able to compete.
Beyond the Ultimate Universe:
* Cosmic entities: Beings of immense power like The Beyonder, Galactus, or Thanos, who operate on a multiversal scale, could easily overcome Superman.
* Other powerful superheroes: Depending on the context and the version of Superman, heroes like the Silver Surfer, Dr. Manhattan, or even a powerful version of the Hulk could challenge him.
Important Considerations:
* Writers and the narrative: Ultimately, the outcome of a battle depends on the writer's intentions and the story they're trying to tell.
* Power levels: Superman's power levels have varied over the years in the Ultimate Universe, making it difficult to say for sure who could beat him.
* Context and rules: The environment, the specific powers at play, and the limitations imposed in a fight all influence the outcome.
It's important to remember that "Ultimate Superman" is a fictional character, and his power levels are constantly evolving. The possibilities are endless in the world of comics!