I will be glad to explain. Dr. Manhattan's power was, to put it in a few words, free control over all aspects of reality (not sure about time, but space was definitely there too). In one word, he was GOD. He was the only character with true superpowers in the Watchmen comics, which imbalanced the whole story heavily - there it was intentional. It is an excellent comic (It's also quite short) by DC I think, and I highly recommend it. There is also a movie, but do me a favor and read the comic first. The movie, while excellent in itself, does not do the comics justice.
And yes, Violet's character. "Reality Control". This power should not be legal in my opinion.