Unknown Soldier, also known as the Nameless Super Soldier or simply Player 1, is one of the two protagonists in the side-scrolling shoot'em up Arcade game Forgotten Worlds. He appears in Marvel vs. Capcom: Clash of Super Heroes as an assist character.
The two warriors have no known name, all they know is how to fight. One day, a powerful being calling himself "Celestial Emperor Bios" started a bid to rule the universe under a new age of violence, and gave life to 8 powerful deities in order to destroy all of civilization. Most of Earth was destroyed in their wake, eventually leaving behind a barren wasteland known as the "Dust World". With all resistance obliterated, the two Unknown Soldiers appeared on Dust World and set upon themselves to stop the evil gods. It's said they were brought here by the people's sorrow, but the truth behind their existence remains unknown.
The Unknown Soldiers wield machine guns and have backup assistance in the form of several flying satellites which provide different types of ranged attacks such as lasers, flamethrowers or other special bullets. They float and move in the air with the help of gravity equipment. Their weapons are provided by Sylphie, a mysterious shopkeeper whose store can appear at any location she desires, even in the middle of enemy territory.
- Cover Fire: Unknown Soldier flies into the screen and quickly shoots a barrage of bullets forward, while a "Laser" satellite near his feet assists by shooting a laser beam. The assist's projectiles have fair speed and power, and provide a good chance for the player to connect other attacks or even Hyper Combos. They can also beat certain other projectiles. It can be used a total of four times. When called to attack, he says Kore demo kurae! (これでも喰らえ！), "Take this!".
- The little satellite accompanying the Unknown Soldier is one of the buyable items available in Forgotten Worlds, sold by Sylphie.
- Unknown Soldier's 2P color (red/orange armor and clothes, dark skin) is the same palette used by the 2nd Unknown Soldier/Player 2 in his origin game.
- The three final bosses from Forgotten Worlds (the God of Wind Whodin, God of Lightning Laidin and Celestial Emperor Bios) appear in the background of the Headquarters of Evil stage. This makes Forgotten Worlds the only series represented only by an assist character to have stage cameos as well.