If you could use any unforgivable curse on any character, who would you curse, with what spell and why???

I would use the killing curse on the death eater who killed Hedwig. Why did they have to kill her. SPARE THE LIFE OF AN INNOCENT OWL, SHE COULD HAVE JUST BEEN DELIVERING A LETTER AND NOT BE ANYTHING TO DO WITH HARRY AT ALL. HOW WOULD THE DEATH EATER HAVE KNOWN WHO'S OWL THAT WAS. HE IS JUST PLAIN EVIL?????!!!!!