Doom is the original Slugfest champion, and thus the Slugfest is somewhat named in his honor.
Victor Von Doom is one of the oldest and most infamous villains in the Marvel Universe. Though he has been defeated throughout the years, he maintains a serious threat to the world. He was college mates with Tony Stark and Reed Richards (Mr. Fantastic) and possesses a scientific mond easily on their levels (though he will steadfastly claim to be their superior).
Doom's most prominant weapon is his armor, which is on the level of Stark's main Iron Man armors (though he will steadfastly claim to have its superior). Like Stark, Doom has several armors with different abilities for various purposes. Common weapons include concussion blasts, electromagnetics, and superhuman strength. The suit can fly,a nd is sealed for underwater and space travel. At times, Doom has even been able to travelt hrough time and dimensions.
Doom is also a prominant practicer of arcane arts, and has magic abilities on par with Dr. Strange (though he will steadfastly claim to be his superior). He has learned how to transfer his mind into other bodies, use magic lightning, and incorporate other mystic energies.
So in short you have a supergenius with Iron Man level armor and some of the most powerful sorcery skills in the world.

THE icon of superheroes and one of the original costumed comic book characters. Baby Kal-El was one of the last surviving members of the planet Krypton, which died a horrible explosive death.
Due to his kryptonian physiology Superman's powers are fueled by Earth's yellow sun. Under the energy of a yellow sun, Supes has vast superhuman strength, near invulnerability, heat/x-ray vision, and the ability to fly at light-speed. He can also survive in space without the aid of a suit or breathing apparatus.
Superman does have three main weaknesses. The most commonly known one is kryptonite. That will kill him after prolonged exposure. He is also vulnerable to magic attacks and influence. While magic will not kill him in the context that kryptonite will, but it will harm him far more easily than conventional attacks. Last, but not least, exposure to energy from a red sun (the same sun Krypton was under) will deprive him of his powers and turn him into a normal scale human.