Up Smash Attack

Up smash, also known as up smash attack (commonly abbreviated "U-Smash"), is a Smash Attack performed by any character by tapping the control stick upward and pressing A, or (in versus mode) by pressing up on the C-stick. The up smash can be charged by holding down the A button for up to two seconds in conjunction with the C-stick, resulting in higher damage and knockback. If the enemy has heavy damage, it can be easy for the player to Star KO or Screen KO them using these moves.

List of Up Smashes in Super Smash Bros.

List of Up Smashes in Super Smash Bros. Melee

List of Up Smashes in Super Smash Bros. Brawl

Bowser - Hops into the air, hitting with his shell. Very strong knockback with good range.
Captain Falcon - Kicks upwards twice. Strong knockback. Can KO around 105% in Melee and 115% in Brawl.
Charizard - Slashes upward with both wings. Can kill around 115%.
Diddy Kong - Does a weird cartwheel in place, hitting three times. Not very powerful, but a decent combo move. Can be used as a sliding DACUS. The weakest up smash in Brawl.
Dr. Mario - Same as Mario, but with slightly less power, unlike his other moves.
Donkey Kong - Claps overhead. Small hitbox that usually only hits foes directly above him, but great power and fairly fast. Can hit grounded opponents in Brawl.
Falco - Just like Fox's, only weaker (though still pretty strong). Can KO around 125%. Can be used as a sliding DACUS.
Fox - Does a flipping kick above his head. Very powerful and quick, with brutal knockback, critical for KOing foes. A great KO move. Best Up Smash of the Star Fox characters. Can KO most characters around 95%. One of the best Up Smashes in the game due to its speed and power. Two fully charged Fox's Up Smashes can Star KO an opponent with 0% damage.
Ganondorf - In SSBM, he kicks twice upward powerfully. In Brawl, he kicks once but it hits all the way to the ground. Has a huge amount of IASA Frames in Brawl. High knockback and KOs around 105%.
Ice Climbers - Slam their hammers above their heads. Not very powerful.
Ike - Swings sword above his head. Covers great range and is powerful but incredibly laggy like almost all of Ike's other attacks. Very strong and can KO near 110%.
Ivysaur - Powder erupts from his bulb. Arguably the best Up Smash in terms of power, being able to KO at percentages as low as 32%, but suffers from long startup lag.
Jigglypuff - Headbutts above itself. Can be used as a sliding DACUS. Fairly strong enough to KO around 115%.
King Dedede - Swings hammer over his head. Less knockback than up tilt. (When uncharged)
Kirby - Does a backflip, kicking. Hits all the way around Kirby. Strong with quick speed. Can KO at 105%.
Link - Slashes over his head three times. Third hit has most knockback. Mostly used to rack up damage. Can be used as a sliding DACUS.
Lucario - Punches upwards with blue aura energy. High range.
Lucas - Releases an extremely powerful blast of PSI above him. Second strongest up smash in the game, but very high start-up and ending lag. Can KO as low as 70%.
Luigi - Headbutts upward. KOs around 113%-115%.
Mario - Headbutts upward. Similar to Luigi's but with less knockback. Can KO most characters around 125%-130%.
Marth - Stabs his sword above his head.
Meta Knight - Slashes above him a few times. Similar to Link's, only much faster and not as powerful. Can KO at 140% onward.
Mewtwo - Holds hand in the air, emitting a spiral of shadowy energy from it. Multiple hits makes it one of his better moves.
Mr. Game & Watch - Headbutts above him wearing a scuba helmet from Octopus. Has a fair amount of start-up lag. Very strong and can KO as low as 80%. It is the third strongest up smash KO percentage wise.
Ness - Does an "Around the World" with his yo-yo, arcing it above him. Weaker than most Up Smashes. Yo-yo can also damage while charging up. Interestingly, when it's 'charging' it doesn't increase in damage or knockback.
Olimar - Throws a Pikmin into the air. Purple Pikmin have the strongest KO power, KOing enemies under 100%.
Peach - Thrusts her arm up quickly. Very powerful when sweetspotted, but very weak when not sweetspotted. If Peach sweetspotted (Peach's body, as opposed to the arm) an opponent with fully charged Up Smash, it can KO at 50% (When it does 23% damage). Uncharged, KOs around 85% when sweetspotted.
Pichu - A powerful headbutt that is one of Pichu's best KO moves and combo set ups.
Pikachu - Flips over, hitting with its tail. Similar to Fox's, but with less range and even faster. Good knockback.
Pit - Slashes above him with both of his swords. KOs near 140%.
R.O.B. - Does a handstand, shooting a burst from his thrusters into the air. His most powerful finisher.
Roy - Same as Marth although with flames surrounding his sword, hitting multiple times. Can spike if sweetspotted at the tip of the sword.
Samus - Uses her arm cannon and shoots fire above her head, hitting five times. Very weak knockback, perhaps the weakest of all up smashes, but does a lot of damage if all hits connect.
Sheik - Pulls with both hands to her sides in a downward way. Does a great deal of damage and knockback when sweetspotted. Not very difficult to sweetspot. Can be used as a sliding DACUS.
Snake - Fires a mortar into the air; more charge, more distance. Can be used as a sliding DACUS, which is probably the most well-known DACUS of all characters.
Sonic - Jumps into the air, spinning in a ball. Has a few invincibility frames. Low knockback, though last hits can Meteor Smash.
Squirtle - Slams hands onto the ground, sending twin geysers into the air. Very powerful, enough to KO around 105%.
Toon Link - Slashes above his head once with his sword. More powerful than Link's and could be his best finisher.
Wario - Spins in place and headbutts upward, hitting multiple times. Can be used as a sliding DACUS.
Wolf - Does a flipping scissor kick above his head, KOing around 120%. Can be used as a sliding DACUS.
Yoshi - Headbutts above himself. Moderate knockback and can KO around 130%.
Young Link - Same as Link, but with less knockback.
Zelda - Waves her hand above her head with magical energy. Comes out quickly, pulls opponents in and has a lot of hits, not to mention the great damage and knockback. At low damage, this can be used multiple times.
Zero Suit Samus - Twirls her whip above her head. Doesn't have much startup lag and has great vertical range. Great for racking up damage. Only the tip does a lot of knockback.

List of Up Smashes in Super Smash Bros. for Nintendo 3DS and Wii U

Mario: Does a head-butt.
Luigi: Does a head-butt.
Peach: Twirls around with one arm thrusting upwards and a ribbon twirling around her.
Bowser: Leaps upwards, hitting with his spiked shell.
Rosalina and Luma: Swipes upwards with her wand.
Bowser Jr.: Does a handstand and spins the propeller on his clown car rapidly.
Donkey Kong: Claps his hands over his head.
Diddy Kong: Does a flip kick, then an upwards hand slap, then finishes with an uppercut.
Yoshi: Does a flip kick.
Wario: Does a head-butt.
Dr. Mario: Does a head-butt.
Link: Slashes overhead three times with his sword.
Zelda: Waves her hand over her head with magic sparkling from it.
Sheik: Thrusts her arms from above her to each side.
Ganondorf: Performs a high-kick.
Toon Link: Slashes his sword overhead.
Samus: Fires explosions in an arc above her.
Zero Suit Samus: Spins around, twirling her plasma whip above her.
Pit: Slashes upwards three times.
Palutena: Erects a pillar of light in front of her.
Dark Pit: Slashes upwards three times.
R.O.B.: Does a head stand and blasts his burner upwards.
Kirby: Does a flip kick.
Meta Knight: Slashes upwards three times.
King Dedede: Swings his hammer overhead.
Captain Olimar: Tosses a Pikmin upwards.
Fox: Does a flip kick.
Falco: Does a flip kick. Hits twice.
Captain Falcon: Performs a high double kick.
Pikachu: Flips over, striking with his tail.
Charizard: Slashes above with both wings, hitting twice.
Greninja: Slashes two water swords above him.
Lucario: Thrusts one arm upwards, aura blasting from his palm.
Jigglypuff: Does a head-butt.
Mewtwo: Summons a storm of dark energy overhead.
Marth: Stabs his sword upwards.
Ike: Does a wide slash above.
Lucina: Stabs her sword upwards.
Robin: Stabs the Levin Sword upwards; when Levin Sword's use expires, the Bronze Sword is used instead.
Roy: Stabs his sword upwards, flames erupting from the blade.
Ness: Does 'Around the World' with his yo-yo.
Lucas: Blasts a large hexagonal PSI burst above him. The most powerful up smash in the game.
Mr. Game & Watch: Puts on a diver helmet and headbutts upwards.
Little Mac: Does a hooking punch overhead.
Duck Hunt: Blasts three shots above with the NES Zapper.
Wii Fit Trainer: Does the 'Tree' pose, hitting above with her arms.
Villager: Sets off fireworks that explode above him.
Shulk: Activates the Monado's beam, stabbing upwards with the energy blade.
Sonic: Leaps upwards and spins around.
Mega Man: Transforms his arms into electrodes and puts them together over his head to create a large electric burst.
Pac-Man: Thrusts upwards, the ghost Inky appearing.
Ryu: Performs a powerful uppercut.
Mii Brawler: Does a flip kick.
Mii Swordfighter: Slashes upwards three times.
Mii Gunner: Blasts explosions in an arc above. Similar to Samus' up smash.

Notable Up Smashes include

Peach's Up Smash has the highest KO potential of all of Peach's attacks at 50%, if sweetspotted (Peach's body, as opposed to the arm when it does 23% damage with fully charged and giving powerful vertical knockback) depending on the stage.
Mr. Game & Watch's Up Smash is the third strongest in the game, and can KO rather quickly, depending on the character and stage.
Lucas's Up Smash has the second highest knockback in Brawl.
Ivysaur's Up Smash can KO at percentages as low as 32%, and it has strongest knockback scaling of all Up Smashes in Brawl.
Mewtwo's Up Smash has a multiple hits that makes one of his better moves.
Ness' Up Smash is the only one that does damage while held, and doesn't become more powerful if charged. It also can't be charged over an edge.