You have to defeat the entire lineup first

Squint a little and you’ll see it

That’s your Custom Character

That’s Noob Saibot. To unlock him you need to:

• Choose Pete Hegseth as your P1 character
• Immediately before the first round begins (the instant the “Fight!” prompt is about to appear), hold the following buttons simultaneously: Back + Low Punch + Low Kick + High Punch + Block.

If you were to collect ALL their melanin and concentrate it into one person, even then I doubt he/she would look much different from the source material.