LogFAQs > #979428226

I'll try and explain this in a way that doesn't require you to play the game.

You have a standard JRPG party, and one of those characters can summon "aeons" to help fight. These are basically giant monsters that totally decimate and make the game easy-mode for people that don't want to grind too much. This is true for everything except the very end game optional bosses, and FFX has a lot of those, and they are very hard. Most of the aeons you get are picked up normally through a standard playthrough. They have fairly ordinary attacks - hit physically, do magic, here's an ultimate attack, etc.

And then there's Yojimbo. Yojimbo is found buried in an optional dungeon. To get him you have to pay a pretty ridiculously high amount of money (for a standard playthrough). Even if you get him, he'll seem really odd to actually use. He doesn't have normal attacks. Instead you pay him money and he seems to decide what attack to use based on what you pay, but for the most part it seems random.

So it's completely reasonable to think that most people who've played this game either never found Yojimbo or never used him once they did.

But there are two interesting things about the guy. The first is that he has this one attack that has the ability to one-hit kill literally any enemy in the game, including the God-like post-game optional end boss that takes a fully maxed out party about 40 minutes to kill ordinarily. The second is that the in-game formula that decides whether he can use this ultimate attack is so fucking complicated that someone wrote a gamefaqs guide that reads a bit like a mathematics research paper.

https://gamefaqs.gamespot.com/ps2/197344-final-fantasy-x/faqs/24392

In a nutshell, there's a ludicrously complicated interplay between how much Yojimbo likes you, what actions you've asked him to do previously, what level the enemy is that you're fighting, what resistance they have to his insta-kill attack and finally a huge amount of RNG. This stuff is so complicated that even only as recent as a couple of years ago people have been breaking open the game's source code to better understand how it's calculated.

An entire guide to just explain how to use ONE attack for one entirely optional assistance character.

It's just bonkers to think that back in 1999 Square decided to put this much work into something so totally unimportant to the game and then hid it completely.