Go read the wiki on existentialism you dumbfucks.
Nietzsche was all about 'God is dead', ergo creating NEW morality, the 'will to power'. Not once does Light say that his mores are his own, he is merely upholding the mores of his society. He's a sheep, if anything.
>what? how do you explain 'bad faith' or 'being-for-others' if neither exists in existentialism?
Thats Sartre's tack on to existentialism. 'bad faith', denying that you are authentically the cause of all your actions, is AFTER THE ABYSS.
The abyss is a central part of existentialism, when you find out that all your beliefs are made up and empty, specifically that your ideas are abstracts instead of having any real meaning.
I've spent far too much time reading this stuff, you don't have to take me at my word but please look into it, as you clearly don't know what you are talking about.