I say:
1. Electric chair
2. Hanging
3. Lethal injection
A firing squad would seem more appropriate in this case.
I offer no objection.
Drawing and quartering would be a hoot to watch.
He should be treated as the Apaches once did. Strip him naked and stake him out on the ground over one of those huge red ant hills in southern NM or AZ - make a few dozen shallow cuts on his arms, legs, torso and eyes, then leave him there.
The ants will make him quite miserable - but the buzzards that would tear him apart bit by bit would be the most fitting.
That's normally called inhuman - but in this case it appears justified to me, because of his own inhumanity.