One of the most interesting superheroes I have seen is Doctor Manhattan/Jon Osterman from Watchmen. The reason for this is because he represents how gaining superhuman abilities could affect a person psychologically. Not only could Doctor Manhattan manipulate matter itself, but he could also see his past, present, and future simultaneously. All of his knowledge and power made him become detached from the rest of humanity.
In addition, Doctor Manhattan represents what could happen if the government took advantage of superhuman individuals because Doctor Manhattan’s power was so great that the United States government made him the lynchpin to their strategic superiority over the Soviet Union during an alternate version of the cold War. This would imply that a government would be willing to turn any superhuman into a weapon.
Overall, I like Doctor Manhattan for his complexity and power. If you are looking for a character who struggles with the weight of his own power, this is the man to see.