Item description:

For both the beetle-saturn and Kronos core in RetroArch. Simply extract to the folder you have designated for saves on RetroArch! :)

Fighters' Megamix has characters you unlock by simply completing the game, much like the earlier Tekken games and the first Soul Calibur on Dreamcast. These characters are the ones that are unlocked for sure.

Any of the hidden characters like the palm tree, or the ones that require the player to hold a button on a particular fighter to select them are not who's unlocked here. The palm tree character requires one to put in 80-something hours into the game. Whether that means you can just let the game sit on the options screen for a while, or it means playing literally 80 hours of this game nonstop isn't something I've ever been able to get clarified, especially since, thanks to the Saturn's poor performance in the states back in the day, there's not as many people discussing specifics in-depth.

Either way, this should eliminate the grind of unlocking most of the characters.