I don't know if you are doing the mission for the first time or not but the way I did it was went super vegeta had vegetas z soul and ultimate attack and made vegeta my master for the z assist and kept spamming the ultimate attack and when I got to the end took them out one at a time and after super vegeta ran out went through the portal use maximum charge to rebuild my ki and if needed used a health capsule repeated until I won.
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All I do on that mission is spam my ultimate because that's all they do