It always bothers me how people take the quote "I am become death, destroyer of worlds" completely out of context. If I recall the point is that Arjuna doesn't want to fight his own family, and Vishnu is pushing him to fight. So in that context you could see Oppenheimer's famous quote as a sad thing. Yes he's created this great power, but he knows it'll be used on other humans. He doesn't want to unleash this death, but he feels compelled by a greater power. Thus in his internal conflict the quote changes almost to reluctant acceptance of what must happen.