The length of time you spend with a character is rarely what gets you attached to them. Shows like Law and Order were on for decades, yet I couldn't tell you thing one about anyone on that show. Similarly, Mario has been the mascot for all of gaming ever since the 80's, but he's hardly everyone's favorite Mario character.
It isn't the time with the character, it's the character in the time.
Every gaming story that sticks with people has had at least one character that fans absolutely fell in love with, despite the fact that by all accounts, they're not in the story, or the game for that matter, for very long.
Whether it's due to their story arc just being the best of the bunch, their character being memorably entertaining, or just because they're really hot, every game fandom has a character that's only known for one specific moment within a single game's narrative, but that moment stuck itself so deep into people's minds that they would never be forgotten.
10. Psycho Mantis - Metal Gear Solid
What the Flowey boss fight did for Zoomer gamers, the Psycho mantis boss fight did for Millennial gamers.
Metal Gear as a franchise is known for their wacky, Game of Death style boss fights where everyone has a wacky as f$ck name, gimmick, and tragic backstory that you learn upon killing them despite knowing earlier likely making the deaths have more impact but that's neither here nor there. Psycho Mantis is no different, in fact up to his fight, character wise, he isn't even the most interesting of the bunch.
But then you get to his fight and this guy permanently sears himself into the psyche of an entire generation of gamers.
Everyone already knows what makes the Psycho Mantis fight so great. For one, when you fight this boss the first time, you'll be shocked to find that you can't move Snake at all. This is because you need to move the controller to the player 2 port in this fight. He then reads your memory card and mocks you depending on which game file he finds there.
Psycho Mantis was a revolutionary boss fight for his time, paving the way for future boss fights like The End in MGS3 and Flowey in Undertale. No wonder we still remember him to this day.