Nope. 2 and after can be completed without killing anyone. Even if you do decide to kill it's not all that violent. We don't know much about Revengeance, which is why I don't see what's up with all the b*tching, so as far as we know it can be completed without killing anyone too. We have to wait for Konami and Platinum to tell us more about the game.
But I honestly don't think Raiden is the Snake type anyway. Even when I was playing 2 he didn't seem fit for the sneak around in a box type of style. Especially after he got his blade.