Of all the alien species that Star Trek created in its nearly 60-year history, the Klingons have been redefined the most frequently. In the Klingons’ first appearance in Star Trek: The Original Series season 1, episode 26, “Errand of Mercy”, Klingon leader Kor (John Colicos) was a military strategist hungry for a “glorious” war, and a narrative foil to Captain James T. Kirk’s (William Shatner) more diplomatic approach. Colicos’ portrayal of Kor set the standard for the Klingons in Star Trek: The Original Series as tyrannical, warmongering adversaries without honor, compared to the integrity of Starfleet officers.
https://screenrant.com/star-trek-redefined-klingons-movies-tv-shows/