If they new about vog and crota then the Guardians would know about the dragon balls. Also lore wise Atheon is unbeatable. And crota in is true form not his crota's end form is invincible.
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Yet he could only swing a sword. Goku and Vegeta can tank and dish out planet destroying attacks on a whim crota cant. Also I'm pretty sure lore wise Eris Morns team put him in that condition so ergo not invincible. But I could be wrong. Still no match for them though.