Aku

Maybe this is in a reality where Jack was killed by Aku's forces.

Aku now stands unopposed, and continues his destructive ways until all life on Earth has gone extinct as well as many other life forms on alien planets. 

Here he stands looking at the ruins of his once vast empire, feeling nothing at all. No sorrow, no regret, not even satisfaction. He just feels... nothing. The fun of causing destruction and cruelty to others has been long gone. Now he wonders if he should get Jack's sword and just do it himself...