alternative ways to say "who are you?"? For saying who are you? I understand you can say Kimi wa dare nanda? or Anata wa dare? and similars. Then what does Silver Fang say here? What I hear is "Dare ja ne .. kimi wa" I guess I'm misshearing a lot because as far as I know "ja ne" it's a way to say good bye so it doesnt make sense to be there? What is he saying exactly?

You're not mishearing it. The is a corrupted form of common to accented speech in Japan. does something similar, but uses . The works as similarly to (question-indicating sentence final particle), but I would think of it as a softer, more colloquial .

(In Shoko's comment on this answer, she suggests that it feels a little bit arrogant and is most likely to come from an old man.)

If is "Who are you?", you can think of as "Who da... hell're you?" or similar.