Master Hand (SSBU)
In Classic Mode
Master Hand appears as a boss in Classic Mode. For the first time since the original Super Smash Bros., Master Hand has the ability to face in either direction (left or right), which he combines with snapping his fingers to teleport around. Also for the first time in the series since Brawl's Boss Battles, Master Hand no longer has a stamina HP indicator, instead having a health bar akin to bosses from Subspace Emissary or World of Light. This results in Crazy Hand having a separate health bar as well, meaning that they no longer share the same pool of HP as they did in Smash 4. However, he can now be stunned, which renders him immobile on the ground for about 8 seconds.
Unlike other installments, not every fighter battles with Master Hand at the end of their Classic Mode route. Mario, Link, Yoshi, Kirby, Luigi, Captain Falcon, Jigglypuff, Bowser, Zelda, Marth, Young Link, Dark Pit, Snake, R.O.B, Toon Link, Wolf, Mega Man, Rosalina & Luma, Pac-Man, Duck Hunt, Bayonetta, Inkling, Simon, Richter, King K. Rool, Piranha Plant, Hero, Terry and Min Min all face someone other than Master Hand at the end of their route. Falco and Ken only fight Master Hand along with Crazy Hand if the intensity is 7.0 or above. Some fighters like Pikachu first fight Mewtwo before facing Master Hand. All the fighters who fight Master Hand, except for Pikachu and Pokémon Trainer, fight both of Master and Crazy Hand if the intensity is 7.0 or above. Ice Climbers, Mewtwo, Chrom, Meta Knight, Pit, Diddy Kong, Ryu, Incineroar, Banjo & Kazooie and Byleth always fight both of the Hands.
Master Hand has received the greatest overhaul of any incarnation, gaining a significantly larger moveset overall. Moves that can be used while Master Hand is playable in World of Light are marked based on their input.
In combination with Crazy Hand
Role in World of Light
In the mode's introductory cinematic, an army of many Master Hands is seen attacking the fighters alongside new foe Galeem. The Master Hands transform into glowing, energy-like forms which are absorbed by Galeem before it unleashes a blast of light that destroys the fighters except for Kirby.
Master Hand can also be seen on the mode's overworld map, interfering with the player's path by creating force fields and destroying bridges. One is confronted before the player fights Galeem. After Galeem's initial defeat, Dharkon appears with his Crazy Hand army who begins to eradicate the Master Hands. When Galeem returns after the players initially defeat Dharkon, two more Master Hands are fought.
Once the player manages to get the true ending's requirements, Master Hand and Crazy Hand are freed and they help the player by using their Static Discharge joint technique to create a giant rift in the map, which Master Hand enters, leading to the penultimate level where Master Hand himself is made into a playable character, engaging in a Mob Smash against 50 light and dark puppet fighters. The only puppet fighters used in this battle are Mario, Link, Samus, Meta Knight, Snake, Sonic, Cloud, and King K. Rool.
Master Hand's freedom suggests that, like the fighters, he was captured by Galeem before the events of World of Light and then cloned into controllable puppets.