PMG appears in 4 Columbo episodes, but I feel that his character as Col. Rumford shows the most ruthless, un-remorseful killing of all 4. Even after Columbo uncovers the truth, Rumford tells him that it "had to be done."
Not only that, but this "patriot" and "man of principle" tried to frame an innocent man for the crime. (Cadet Springer)