A .44 magnum close range right between the eyes, he wouldn’t feel a thing. Liberals are scumbags; they aren’t interested in preventing suffering in those who are guilty but in prolonging it in those who are innocent, namely, the families. The innocent are their favorite targets.
In a similar vein, so to speak, one could also use a combination of that has been used to carry out a death sentence in the past. How about a lead and copper cocktail?