impetuous
(adj.) rash; hastily done (Hilda’s hasty slaying of the king was an impetuous, thoughtless action.)

mendacious
(adj.) having a lying, false character (The mendacious content of the tabloid magazines is at least entertaining.)

proclivity
(n.) a strong inclination toward something (In a sick twist of fate, Harold’s childhood proclivity for torturing small animals grew into a desire to become a surgeon.)