Didn't Quite Think This Through
In the middle of kicking Phoenix into the sun, Wizard declared, "There will be no finale for you."
Haruto then reverted to his civilian self and went about talking with Rinko to see if she was all right.
Meanwhile, as Phoenix fell into the sun, he said, "Well, shit. On the one hand, the sun is going to keep killing me, and my powers make it so I'll keep resurrecting."
On resurrecting, he continued, "On the other hand, I also become even more powerful when I come back than I was when I died."
Coming back a third time, he added, "So if I just wait about a week or so, I should probably have died and resurrected enough times to just blow up the sun."
The sun refrained to comment, other than burning him to a crisp again. By this point, Phoenix was resurrecting so quickly that he dying didn't even interrupt his sentences. "Once I don't have this giant ball of superheated gas killing me anymore, I'll just fly to Earth, kick that ringed wizard's ass, and... I dunno, take over the world and make everyone fight each other until there's someone strong enough to fight me. Or something."
Of course, the sun is really, really, really big, so Phoenix was slightly off in his estimate. It took two weeks of constantly dying and resurrecting before he could blow it up.
And then everything on Earth began dying out without solar light and heat to sustain it, until the crossover movie reset the universe.