Okay so I'm trying to kill Fafnir, my main 3 party members are level 63, 60 and 60...Is it possible for me to kill him at this level?

I don't seem to even damage him (I know he has a lot of HP but it doesnt seem to go down after many many attacks).

Only have about 3 marks left before the final 50 million HP or whatever it is monster. :P