Goku can (and has) died (twice that I know of), and had to be revived with the dragon balls (*snicker* *snicker* "balls!"). Guardians can be revived as many times as necessary without the gathering of dragon balls. Goku's strength would exhaust as guardians overwhelm him.
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Kill their ghosts. Done.
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And this is how you make sure a guardian stays dead
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Don't think guardians can be revived if their bodies are disintegrated...
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Guardians bodies disintegrate after a short time anyway, it would just be sooner rather than later .
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How would the guardians overwhelm him? Wtf are you smoking?
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Strength in numbers. Sure, he can deflect the first couple gallerhorn blasts, dodge an onslaught of nova bombs, and shake off bullets like dead skin. He can't keep it up forever, he will get tired, and when he does; the hits will start taking their toll. Guardians are tireless machines of war, and there's a lot of them. Goku can't constantly defend himself, no matter how many levels of super sayin there is. He can't stop a re spawning army of guardians.
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Except goku could just lead off the battle with an earth sized nova bomb wiping every guardian into extinction
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Bro he would literally air their as they attempt to hurt him. Planet vaporizing hits don't even scratch him