The prophet Samuel, appears to have disagreed with that opinion on behalf of his Lord. He dispatched the murderous tyrant.
Saul took the murderer King Agag of the Amalekites alive, Because of that "humility" in the face of evil, Saul came to lose his kingship. Samuel came and rebuked Saul. Samuel then said to Agag, "Your sword has made women childless, so your mother shall be childless among women." Samuel then executed Agag directly.
However in the short time Agag was held, he did manage to father children, and the line of theAmalikites continues afflicting us all to this day.
Like I said, I am not categorically against the death penalty. I wouldn't expect a soldier or guard to put their life in harms way to keep an evil person alive.
But the commission from our Lord to baptise the nations is very powerful, as is his grace. The Lord didn't qualify his statement with "only nations that are gentle and harmless." Each soul saved is a great and joyous victory for heaven, and a crushing defeat for evil.
If it was up to me, I would use the death penalty as an instrument of cival authority very rarely.