Board Thread:Questions and Answers/@comment-97641-20170724191440/@comment-97641-20170724193833

I don't know what NLF means

Indestructible means someone with armor, skin or whatever that cannot be harmed; yet if this was bypassed they can be killed.

Unkillable means the character can be as squishy as a sponge but cannot die from anything conventional. Aku is clearly not indestructible, you can cut him with a normal sword: it's just irrelevant to his shadow body.