qualm [qualms](prick of the conscience, moral scrupule) noun [UK: kwɑːm] [US: kwɑːm]
scruple [scruples](hesitation from the difficulty of determining what is right) noun [UK: ˈskruːp.l̩] [US: ˈskruːp.l̩]He has no scruples about lying. = Él no tiene escrúpulos para mentir.
sin escrúpulos adjective
unprincipled(lacking moral values) adjective [UK: ʌn.ˈprɪn.səp.l̩d] [US: ʌn.ˈprɪn.səp.l̩d]