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.
It's a matter of debate. Some might argue there are other characters with equally or more powerful abilities. But Dr Manhattan's powers are indeed incredibly vast and might put him at the top for many.
The themes explored in this graphic novel are quite profound. There is the theme of power and its consequences. Dr Manhattan's power makes him almost omnipotent, yet he struggles with his own sense of purpose and connection to others. Ozymandias' pursuit of power through his elaborate plan also has far - reaching implications. Another theme is the nature of heroism. Are Ozymandias' actions, although aimed at what he believes is the greater good, heroic? And what about Dr Manhattan? His power could be used for great good, but he seems to be more of a bystander in many situations.
In a 'dr manhattan x reader fanfic', the setting could range from the post - apocalyptic world of the Watchmen universe to more contemporary or even alternate settings. The relationship might be one of admiration from the reader's side, as Dr. Manhattan represents an entity beyond human comprehension. It may also explore themes of power imbalance and how the reader tries to bridge the gap between their mortal self and Dr. Manhattan's omnipotent being.