They can only die due to the actions of others, Kabr used his light to penetrate the Vault of Glass, I don't think Goku could kill Atheon, Crota can only be harmed by his own sword, I doubt Goku is clever enough to find that out, Gorgons, he will die immediately, The Templar, perhaps he has a chance against this one. Goku could possibly kill all guardians but the enemies we fight we only killed because of team work, Goku is solo <.<