How is Krona defeated? Hal freaking kills him, that’s how!
The only odd thing here is that…a Green Lantern ring is incapable of killing a Guardian. This shouldn’t be possible.
I mean, it’s nice, that someone could actually stop the uber powerful bad guy of doom, but for some reason it seems like the Guardians were prepared to just bend over and let everyone get slaughtered if a fellow Guardian ever turned evil.
