I think George Kennedy was an excellent actor. He could come across totally friendly and believable and at the drop of a hat turn cold and menacing.
He was VERY versatile in that way.
Totally friendly, a real hero - I think of his role as Joe Petrone in the Airport movies. You couldn't help but love him.
Cold and Menacing - his roles in The Sons of Katie Elder and Cahill: US Marshall (he was particularly menacing, in fact downright frightening, in this one).
Mrs. C