Heh, forgot to vote. Also, is it Son or Sun? Also how curious how he beat Dark Phoenix
IIRC, he killed his Universe's avatar of the Phoenix Force before coming to the main Marvel universe, so it was off-panel. Note that he didn't defeat Dark Phoenix, the title of whom refers to an insane Jean Grey channeling the Phoenix force.
TBH, I sort of doubt he could defeat a prime Dark Phoenix, but any avatar of the PF is pretty powerful.
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"Give him a fair trial. Then shoot him." - Napoleon Bonaparte after the capture of Andreas Hofer