Going off the assumption you have 3 turns to kill him, trying to play with some math:
@ 1,503,750 hp you'd need to do 501,250 a turn
Double Goemon 25x is 20,050 damage per round / 3,342 per character
Double Valk 18x is 27,847 damage per round / 4,541 per character
I think you could...