Daniel Day-Lewis. Incredible actor, and easily capable of playing a cold-blooded murderer - check Gangs of New York and There Will Be Blood.
Christian Bale. Practically his entire filmography involves him playing psychos and deranged killers.
Either one would be a great villain. As for a henchman, I think that's pretty easy. Just find a giant that's already known for playing an evil henchman-type figure.
Hafþór Júlíus Björnsson! Being 6'7" and nearly 400 pounds and one of the strongest people in the world makes for a pretty intimidating person.
