A character is killed off in a particularly gruesome manner and left to be found just to offend or insult someone, or to cause someone serious anguish. The usual victims are those who matter to the hero, specifically best buddies, love interests, and sidekicks.
Brutally killed off for the sake of the protagonist's character development
https://tvtropes.org/pmwiki/pmwiki.php/Main/StuffedIntoTheFridge
Brutally killed off for the sake of the protagonist's character development