That's what I was thinking. If Supes is angry, not holding back, and allowed to speedblitz, I can't see one single GL taking him down by himself, even if it was Hal.
Gl can set their rings to autofire....So thats out.
Truthfully, Flash, WW and GL should do it. Supes trys to blitz WW, flash steals his speed instantly, and while he's stock still, WW slits his throat with her tiara, all in the space of .0001 seconds. Refute that. And so as to prevent a revival, GL turns the yellow sun to a red one, thus ending his existence. Game over....Course, the writers and editors wouldn't allow boy blue to die like that, but its the easiest, quickest route. Then gls disperse his atoms, and return the sun to its orignal yellow, so as to not depower Supergirl.