Well, this is about as serious as we've ever seen Ash and the show get-- as goofy as he is and as irreverent and sloppy as he's always been about fighting evil, he loves Kelly and Brandy enough to kill himself to save them. Unfortunately, the plan didn't work with Kelly, presumably because somebody is currently occupying her body. And it's a good thing that returning from the Rift Dimension automatically heals your wounds, otherwise it would have been a short-lived victory (but why didn't Ash's hand heal, I wonder?).
And I wonder what's going to become of that last Knight of Sumeria? It doesn't look good for her.