The following handy guide was made by the folks at Eurogamer, in regard to unlocking playable characters in Super Smash Bros. Ultimate:
The fastest way to unlock characters in Super Smash Bros Ultimate
Play a Smash match (also known as Versus mode) and after the match is over, you’ll be challenged by a random character so you can unlock them.
There is a ten minute in-game counter between these encounters, designed to slow down to rate of character unlocks. However, you can avoid this by restarting the game. The next time you play a Smash / Versus match, and you’ll then get another character unlock.
You can make this go even quicker is you set it so match settings are set to Stamina, and each character’s stamina being as slow as possible (10), enough so a single projectile will end the match – and saving that as a template for future runs.
If you get to a point where this no longer works, you may need to move a certain distance during at match between unlocks as well – dannyjayes1 on reddit recommends playing on the ‘Moray Towers’ (Splatoon stage), walking up and down, then completing the match.
Doing this method – playing a Smash match, unlocking a character, closing the game and repeating – is a grind, but is the fastest way to go.
Other character unlock methods in Super Smash Bros Ultimate
There are a few other ways to get characters in Super Smash Bros Ultimate:
- Each Classic Mode completion (found in the Games and More portion of the main menu) results in a character unlock. The benefit of this is the eight starting roster will unlock Super Smash Bros characters in a specific order, as shown in the following official image (thanks, Stuart98 on reddit):
- Encounter the respective character when playing World of Light, the game’s single-player adventure, to unlock them across all modes. This is also how you unlock Mii Fighter styles.
- As mentioned in the fastest unlock method above, playing any other mode for ten minutes (of in-game time) will see a New Challenger encounter when you next exit the mode.
Note that if you fail when challenged by a character, then you can attempt again by selecting it on the main menu screen. It’s intermittent, so keep playing until it appears again.
Source: Eurogamer.net