adversary
The definition for adversary is "One who opposes or resists." Used in a sentence: Franklin hoped to defeat his adversary in the afternoon's tennis match.
heinous
The definition for heinous is "Shockingly evil." Used in a sentence: Eduardo's heinous betrayal of Lydia shocked even Latasha, who knew his evil ways.
onset
The definition for onset is "Beginning." Used in a sentence: Crocuses bloom at the onset of spring, sometimes even before the snow melts.
stealth
The definition for stealth is "The act of moving secretly or unnoticed." Used in a sentence: The burglar took the ring by stealth, slipping it from the sleeping woman's finger.
unscrupulous
The definition for unscrupulous is "Lacking principles." Used in a sentence: The unscrupulous salesman was fired for lying to his customers.