Originally Posted by Wing Gundam Zero
1) You have to be in the second playthrough.
i know that, thats what your guide says in the first place but the 3 dots with super vegeta will only appear if you are finished gokus AND vegetas DU once, then cooler will be there on gokus second play.
i just did gokus 2 times in a row and no super vegeta nor cooler, beat it with vegeta (got the achievement only the after the second run) and again with goku and he was there.
so being on gokus 2nd run of DU without having finished vegeta at least once will not trigger the cooler event.