Mastermind defeats Dazzler
Mastermind, a mutant who can project illusions against Dazzler, whose power is to turn sound into light. The location battle is the Blue Area of the Moon and really provides no certain advantage to any individual in this matchup. Simply put, Dazzler is usually regarded as a joke, but I will not do so. However its clear that she is the underdog in this matchup.
Easily said and done, Mastermind creates an illusion in which multiple outcomes are possible. He either subdues her, or kills her by making her go off into space. Were talking about a character in Mastermind that was able to harness the power of the Phoenix and made her join the Hellfire Club inducing the Dark Phoenix.
Also, one thing to consider, not knowing the exact shape of things on the Blue Area of the Moon, there is no sound in space. Therefore, Dazzler has no catalyst for her powers. Though as I said, not knowing the exact shape of the Ble Area of the Moon its shouldnt factor into your decision.
In closing, Dazzler is clearly overmatched here and Mastermind being a much higher level mutant should be able to take this match quite easily.