In the comics, Dr. Manhattan's 'ending' isn't a straightforward death. It's a convoluted series of events tied to his perception of time, reality, and his place in the universe. His existence becomes highly philosophical and ambiguous.
Dr Fate is a significant character in DC. He has a mystical helmet that grants him immense powers and a connection to the forces of magic. He's been a part of various DC storylines and teams.
Dr Fate's age is rather ambiguous in DC Comics. Magic keeps him ageless in a sense. Different story arcs might suggest different ages, but there's no set, clear number.
It depends on your perspective. Some might view Dr. Manhattan as a villain because of the way his powers and choices impact the story and other characters. But others might see him as more of an anti-hero or a morally ambiguous figure.