To be honest, Hal Jordan is a normal human and he also soloed the whole GL corps and guardians just because he had a green latern ring. Also surviving black holes is kinda a staple for comic characters, if not outright a salvation ticket ("remember that giant explosion that looked like it disintregated me? Yeah, turns out it formed a black hole of sorts that put me in some other dimension and now I got back baby!")
EDIT: This site seems to confirm it
"The resulting explosion destroys the mountain and, as far as the Guardians could tell, Doomsday. In actuality, the explosion tore a hole in space itself, sending Doomsday hurtling thousands and thousands of light years away. "
You're forgeting the point where the continent was glassed because they hit the super-reactor that fueled everything in the planet and it super-exploded.
That was propaganda. Superman was geting kinda of stale, so hey let's kill and ressurect him! (plus he never really died, more like he was left in coma)
On the other hand, it helped that doosmday, exceptionally, can make superman bleed with its sharp extremities. Not being an anime character, supes cannot afford to lose multiple gallons of blood. Jack, on the other hand, is an anime character so doosmday cannot kill him with blood loss!