Previous Post Korvac and wife were maybe Skyfather level at best, that's plenty powerful enough to overtake most opponents but if he's put up against a team as Uber and overwhelming as this they simply have zero chance. Superboy-Prime would be challenge enough on his own, they could deal with Doomsday easy but Imperiex?!!! No Chance.

Korvac was so dangerous, as he gained his cosmic powers in the future and then came to the past. No one noticed him as he specificlly kept 'under the radar'.
As powerful as he was, his limits must have been maximum Galactus level as his databanks gave him the power.
He was then planning, without anyone realising he was planning to take over the MU. That is why he was so deadly and Odin et al decided to try and take him out. It was noticable that this was a clear sign of Galactus' superioity over Odin, as a being with a porportion of his power literally made Odin scared enough to beg for help from Zeus and Mephistro and their combined armies.
There was no mention ANYWHERE that Korvac was stealing power from anywhere else.

SMP however is enough to take on Korvac. I rated Corina as around Silver Surfer level, as she was the daughter of an Elder but didn't have any showings. Regular Doomsday gives her a good fight. Whilst the others ensure a win.