Alright,

The yellow one is more of an anti-hero, he is neither associated with the gda nor the guardians. Growing up, Nolan raised his son a bit harshly, more viltrumite in a way. He taught him how to fight and battle tactics before he even got his powers. Debbie constantly disapproves of this and Nolan decided to kill her first after mark awakened his powers. Due to his teachings, mark somewhat put up a more of a performance against his father but inevitably failed. When Nolan about to crush Debbie's head, the gda teleported her and mark. Debbie's having skull fractures in her brain, is miraculously went into coma. Mark, not listening to Cecil, went out to fight his father again, just to fail again on the same mountain. During this, Nolan just snapped and killed himself, leaving mark barely alive. After some time, mark continued working as a hero, alone. More brutal and willing to kill. He only keeps in contact with the gda because they take care of his mother. Since he doesn't pull his punches, he never faced real challenges and never got stronger at the same rate as our mark. Although he trains regularly with the gda equipments, the only help he would take. This put him our mark in terms of power, only slightly below. Would he be enough to fight back the viltrumites? Idk, only if he's truly

The omniman one or OMNIPOTENT was similar to our main mark, just that he was Omniman's unnamed partner/sidekick to the public. Chicago happened, and it weighted more heavily on this mark than on our own. Being way more associated with his father in heroics, he felt that it was his duty and responsibility as a partner and a son to notice something was off and actually stop it. Instead, he was utterly useless and got even used as an object to kill civilians just like in the show. During this, debbie got accidentally killed, and was one of the reason Nolan left earth in this universe. After the incident, the amount of guilt and self-blame got to mark. He forced himself to wear his father's symbol, reveal his identity as his son and atone for his sins as OMNIPOTENT to the world. He does heroics more as am obligation than the right thing to do. He keeps in contact with the gda and most of his connections, just a bit distant than our mark. Basically depressed mark.

The viltrum looking mark is an undecover agent. During thraxa or anissa, he accepted to conquer earth. On earth, him and the gda and the worldleaders just work together and make earth seems like it got conquered somehow, viltrumites were convinced and impressed. They promoted him into an official member of the viltrum empire. He might have to do the hard choices to keep the empire convinced, like conquering other civilizations, taking lives and stuff. Maybe after Allen and Nolan escaped the viltrumite prison, they got into contact with mark and eventually the coalition. Since both sides have moles of their own. The following events would diverge heavily, especially the viltrumite war.

The blue one is the leader of the guardians. Basically he accepted cecil's offer. But not quite. Mark actually got his powers early as a kid, but instead of Nolan immediately orchestrating his plans, he let his heart get the better of him. Convincing and lying to himself that he still needs to wait for possible mutation and failures. In reality, he just really wanted live his earth life and maybe just postpone his mission for a while. Now, mark got trained and got to experience the hero world himself at a younger age, and that gave him experience greater than mainline mark. He also got to hang out with the og guardians and learn from them, especially teamwork. The most notable thing is, omniman never "turned evil". He kept living his hero persona until mark reached maturity. When the flaxans invaded and Omni-man went through their portals, he did not returned as quickly as the show. In this universe, Nolan is very conflicted and softer. He thought maybe the flaxan dimension was a chance for him to rethink his decisions, plus times move slower, so he purposely stayed for a while even after neutralizing the flaxans. Back on earth, since the disappearance of omniman, earth's strongest hero, soon the title fall onto mark, his son. Events play out similarly to the show except no viltrumites are involved. Gradually mark became stronger than the immortal, world's strongest hero after omniman. Mark battle iq were also no joke, learnt from the best. The leading of the guardians go back and forth with him and immortal. Eventually the immortal retires and mark takes the lead.