He sees her body – the body of the woman that tortured his parents, made them lose their minds – lying on the floor, dead. He used to think that knowing she was wiped from the world permanently would give him some sort of relief or quell the yearning for revenge that had grown inside him, but he feels nothing.
He feels nothing for the woman who killed and tortured so many. He feels nothing for her fellow Death Eaters that fell throughout the battle. He feels nothing for the Death Eaters that survived who try to run away and save themselves from Azkaban. Nothing at all.
Instead, he feels grief for those who died as heroes for what is right. He feels sorrow for those who have lost loves ones and are left to fill the holes the dead leave. He feels pain, so much pain, both emotionally and physically, the he cannot feel anything for anyone else.
He feels nothing for her, so he turns away, knowing that later, after visits to St. Mungo's and seeing the shells of what his parents once were once again, satisfaction of her death will come.