O.... dammit, when I finally pay attention, I completely miss the point.that wasnt the agreement, vegeta never agreed to become a god of destruction whis was just saying that initially because he was being sarcastic
the only agreement is that they get food in return for training them


goku is faster than time but but but superman can beat him





maybe Buu? Buu was dumb as shyt pure evil and just wanted to destroy. Mirror that and you get a OP dude like Hit, chill, grown, and catching bodies for the hustle. 
The power......would be inconceivable

. what we do know is that vegeta and goku will go to kaab/caab ( what ever hes called) planet to meet the other sayians