Depends which universe it takes place in. If it take place in the destiny universe, then goku has already lost to the darkness because it has engulfed most of the universe and is still going. He is always the universe's last hope and it seems he failed. If it takes place in the dbz universe then goku has about a 50/50 chance of wining depending on if we kill piccolo first so he cannot be revived or we find the dragon balls and simply wish for invulnerability. We could also give goku an icebreaker and trick him into firing it without ammo in it and it ends up killing him. If we shoot a million ghorns at him , he won't be able to dodge all the wolf packs, even if it misses. Golden guns could kill him probably. Lasers can still hurt him so if anything fusion rifles and the vex can demolish him.... In terms of npcs, Atheon simply needs to teleport him into a time stream and deactivate the sync plates so he is lost forever. That or summon some gorgons