(of, like) a murderer

ruthless

not easy troubled or excited

calm, collected

not sensitive (to touch, light, to the feelings of other people)

indifferent, callous

(of the body) having power, able to do things easily; (of the mind) feeling confident, sure, determined; not easily broken, damaged

healthy, powerful

(of meat) hard to cut or get one's teeth into; not easily cut, broken or worn out; (of a person) strong; able to endure hardship; (of a person) rough and violent

sturdy, strong