heartless

adj

1. Without feeling, emotion, or concern for others; uncaring; cruel.

   “His heartless actions and cold manner left her saddened and feeling alone.”

   “The world is a dangerous, violent place […] and the only true refuge from this heartless world is the family.”

   “It's safer to be heartless than mindless. The history of the world is the history of the triumph of the heartless over the mindless.”

   “Mr. Burns is similarly perfectly cast as a heartless capitalist willing to do anything for a quick buck, even if it means endangering the lives of those around him and Marge elegantly rounds out the main cast as a good, pure-hearted and overly indulgent woman who sees the big, good heart (literally and metaphorically) of a monstrous man-brute.”

2. Without a physical heart.
3. (archaic)Listless, unenthusiastic.

   “Near-synonyms: spiritless, unhearty”

4. (obsolete)Without courage; fearful, cowardly.

   “Cecilia then, though almost heartless, resolved upon talking with Mr. Harrel himself […].”