While most face card operators did plenty of showboating and monologing, the King of Spades is all business, only making his presence known by his blimp or the sound of gunfire. The character is shrouded in mystery, and all that's revealed about his origins is a quick flashback in Season 2, Episode 7.
The source material does reveal more about the character. In the manga, his name is revealed to be Isao Shirabi, a reputable mercenary with next-level skills in weaponry and combat. At one point, he took a job with a fellow soldier-for-fire and friend known as Apache. Shirabi thought it was a bad idea and he turned out to be right: the ill-fated gig resulted in a devastating injury for his combat-ready companion. Apache knew his life would be full of turmoil if he survived, so he begged Shriabi to end his misery and kill him, which was briefly shown in the Netflix series. Shirabi didn't want to but ended up doing it anyway, and the traumatizing event is where he adopted the mindset that life was cruel and that he could save people by ending their pain with death. That's why the King of Spades doesn't see himself as a villain but as a savior freeing those he kills from the agony that life inevitably brings. He prefers going after large groups of players to get higher kill counts faster, and his death-dealing skills are backed by what he believes to be good intentions. Masterful murder abilities and a deranged way of thinking easily make the war-torn persona a heavy favorite for the deadliest boss battle in "Alice in Borderland," who has also garnered some intriguing reactions from fans.
