obdurate

/ˈäb-də-rət/

Middle English, borrowed from Late Latin obdūrātus, going back to Latin, past participle of obdūrāre "to harden, be persistent, hold out," from ob-, perfective prefix + dūrāre "to harden, hold out, endure"

adjective

  1. stubbornly persistent in wrongdoing

  2. hardened in feelings

  3. resistant to persuasion or softening influences

an unrepentant, obdurate sinner

The obdurate enemy was merciless.

inflexible obdurate adamant mean unwilling to alter a predetermined course or purpose. inflexible implies rigid adherence or even servile conformity to principle. obdurate stresses hardness of heart and insensitivity to appeals for mercy or the influence of divine grace.