Yes, and while he surely was guilty of mass genocide, this in and of itself does not make assassinating him "not a sin." Murder is murder........be it one or millions..........justifications such as "for the greater good" don't reflect Scriptural teachings in my opinion. Capture, arrest, charge, put on trial and render verdict, then decide the appropriate punishment, and carry that punishment out would be the better route to take in my opinion.
God reserves "vengeance" for Himself as I recall. Just saying........
I suppose to clarify.....if one were actually standing there when Hitler ordered they be gassed, and they fought back to protect themselves and others, and Hitler were killed in the melee, then that would not be murder, but self defense, and I could accept that.