Can someone tell me why Korvac has the Badoon keyword? If he would have ANY alien race keyword wouldn't it be the Kree?

He was "re-engineered" by the Badoon, and was a sort of pet of theirs.

Fairly certain it was the Kree who ran experiments on him and such....but whatever. My Badoon army welcome this giant tentpole.

I'm going to make a custom switch dial of korvac first 3 clicks with his old wheel chair sculpt before he attained god hood. Then when I hit his stop click, I will switch out the sculpts and give visual aid to my opponents as to what exactly is happening after damaging me. Muwhahahaha

That was only in the cartoon Earth's Mightiest Heroes. In the comics he was a Badoon collaborator who was later punished by them for falling asleep while working and turned into a cyborg, basically.

Just wondering...

Does this mean that if you pulse wave Korvac on this click, you can't ignore his invincible?

Also, if you got hit by Jenny Sparks, or were charged by an Iron Paladin, or were somehow otherwise unable to "use" your defensive power, and went right past this power, would you still have power cosmic afterwards?

Pulse Wave would not work on this power, as everything within the white can't be ignored. As for "Can't use defense" powers being used against him, players guide states "A game effect which states that another game effect can’t be used prevents a new activation of that specified game effect, but it does not end any ongoing effects unless otherwise noted." So I'd say a "can't use defense" effect would prevent Power Cosmic from activating.