The most powerful character in Marvel Comics is often debated. One could make a case for Scarlet Witch, given her reality-warping abilities. However, it's subjective and can change depending on the storylines and interpretations.
In Marvel Comics, there are several contenders for the most powerful character. Some might argue it's Galactus with his cosmic powers, while others might point to Doctor Strange and his mastery of the mystic arts. But ultimately, it depends on how you define 'powerful'.
Well, it's a tough call, but many would say it's the One-Above-All. This character is considered the supreme being in the Marvel multiverse.