Dictionary.com/obdurate:

obdurate (OB-du-rit; OB-dyu-rit) adjective

1. 1. Hardened in wrongdoing or wickedness; stubbornly impenitent: “obdurate conscience of the old sinner” (Sir Walter Scott).
   2. Hardened against feeling; hardhearted: an obdurate miser.
2. Not giving in to persuasion; intractable. See Synonyms at inflexible.

[Middle English obdurat, from Late Latin obdrtus, past participle of obdrre, to harden, from Latin, to be hard, endure : ob-, intensive pref.; see ob- + drus, hard; see deru- in Indo-European Roots.]

Source: The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2000 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.

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adj 1: stubbornly persistent in wrongdoing [syn: cussed, obstinate, unrepentant] 2: showing unfeeling resistance to tender feelings; “the child's misery would move even the most obdurate heart” [syn: flinty, stony]

Source: WordNet ® 2.0, © 2003 Princeton University

This word is late due to a profound and incapacitating flu I am yet suffering. Nonetheless, this word should be fun to use. It should give us plenty excuses to develop our villains.