The Guardians, no matter the differences in power, would be able to slowly wear down Goku. If Goku kills an entire Fireteam, their Ghosts will revive them. They could continue to fight, die, and repeat until Goku finally runs out of energy. If Goku dies, you better hope someone has all seven Dragon Balls. [spoiler]And that Goku can actually be returned to life.[/spoiler]