Marcus is described as a "charming, chiseled, colossus." Much like Luther, his power is his strength, and he's said to be "honest, virtuous, and demanding." He keeps the family together, is graceful but lethal, calculated but compassionate, and unlike the Umbrella Academy's number one, he's as smart as he is strong. Marcus is disciplined, rational, and in control. He oozes confidence and leadership without ever having to raise his voice.
Marcus is only known as Number One in his graphic novel appearance, and he refers to Luther as "brother," a nod to their relationship as two of the 43 children born under curious circumstances on 1 October, 1989. From his description, he seems to be a more level-headed leader than his counterpart and notably hasn't been modified the same way. It looks like Reginald learned his lesson about using risky procedures on his children.