I thought it important to discuss this rare, but important phenomena. The critical hit of usmash.
The best way I can describe the uber spot of Peach's usmash is that it's a small sphere located roughly at Peach's upraised shoulder. It hits for 19% uncharged and is just shy of the KO power of Fox's usmash, but this attack sends foes straight up instead of slightly off-center. Either way it's Peach most powerful KO move by far aside from bombs and death turnips.
The screwy thing with this hitbox is that, because the volume it takes up is so much less than that the other 3 hitboxes, it takes critical positioning to get it off without the uppermost hitbox taking priority over it. Even if your target happens to be in both the 15% hitbox and the 19% hitbox, the 15% hit will take precedence over the 19%. This adds to the critical spacing needed to connect with this move. In a real match, usmash isn't something that you can spam, so it takes very precise setups to go about hitting with this otherwise godly power hit. Since this is essentially the only uber-powerful move Peach has, we might as well share our knowledge on how to hit with it when possible.
Shield breaks: Virtually any character can be sweetspotted with usmash on a shield break if you time it right. The timing and positioning of Peach varies due to constantly moving body of your shield broken opponent, and often involves very specific timing (practice, practice). Kirby, Pikachu (but not Pichu), and Jigglypuff cannot be hit from a shield broken state, they are too short. Being directly below them on a sloped surface is the only way to connect with it.
How do you shield break? Skillful use of Mr. Saturn, or death turnips. Hey, it's more than what other people get, and if you do break their shield, you get a chance to really punish a la Fox.
Team Play: When your teammate has caught someone in a grab, it's also easy to shoulderpad the grabbed enemy. Position yourself so that the enemy is in between you and your teammate, and usmash. More often than not you'll get a shoulderpad out of it. Again, practice and see. Fox and Peach are quite deadly this way, both being capable of usmash killing when either one gets a grab.
http://www.youtube.com/watch?v=qbAOsQo4aKY <-example here
*Several dash attacks can also be punished by usmash when shielded. They're already running into you so half the setup is done. Prime examples of who can fall to this are Jigglypuff, Peach, Zelda, Samus, and more that I can't confirm at the moment. Be aware that you need at least 13 frames of advantage for this to work, assuming your timing is perfect.
Many characters can also be hit if you chase their rolls perfectly. Any type of roll can be punished. A tech roll, ledge roll, etc. This works when they manage to roll into you, but not past you. More oten than not they'll wind up into the shoulderpad.
If your opponent DIs your dthrow incorrectly (towards you instead of away) and you usmash in response, the sweet spot is capable of connecting. Like against Roy, Ganon, Sheik or others with similar fall speeds. They need about 100ish damage racked up first.
From dtilts with no DI
The 3 fast fallers fall so quickly that, after being dtilted at certain damage levels, they'll fall right into the usmash sweetspot without being able to escape. You can charge it up, and if you release it at the right time, it will sweet spot and KILL. However, they need to not DI the dtilt.
Fox: starting at 70 and up to 85 (roughly), connecting with a dtilt that isn't DI'd will pop Fox up into the air and fall, and leave him stunned enough so that he falls right into the usmash sweet spot (you may have to dash over a bit first). These two moves wind up doing about 32-34 damage, and gets vertical KOs below 110%.
Falco: add about 3 damage to Fox's figures.
Falcon: Works from a little under 80 to slightly 90, I can best gather.
There are several other numbers on characters where you can dtilt-usmash, but I'm too lazy to figure them out. They're all low figures, so they won't lead to kills.
Jiggs: both her dash attack and her Pound leave her vulnerable to usmash when you shield it. dash attack almost assuredly leaves the puff getting sweetspotted, while the Pound is dependent on her position.
If Jigglypuff misses a Rest, you cannot normally punish her with a shoulder pad. However, if she is on a significant slope (the ones on DK64 are enough), you can get under her and hit with it when you turn your back. Push her a little to the slope if you have to.
Ganondorf: Works when Ganondorf misses his ground Down+B and you're inside him.
Sheik: You can punish her Vanish lag with this! http://www.youtube.com/watch?v=CDcBFA5beMI
However, it is much harder than the vid makes it appear.
1. You must be right next to her, with back-turned for the sweetspot to hit.
2. The usmash must connect 25-29 frames after Sheik lands. Too soon and it won't sweetspot. Too late, and Sheik can act.
3. Pivoting an usmash is not easy on the fly.
I'm not quite done, but help me out here, guys.
The best way I can describe the uber spot of Peach's usmash is that it's a small sphere located roughly at Peach's upraised shoulder. It hits for 19% uncharged and is just shy of the KO power of Fox's usmash, but this attack sends foes straight up instead of slightly off-center. Either way it's Peach most powerful KO move by far aside from bombs and death turnips.
The screwy thing with this hitbox is that, because the volume it takes up is so much less than that the other 3 hitboxes, it takes critical positioning to get it off without the uppermost hitbox taking priority over it. Even if your target happens to be in both the 15% hitbox and the 19% hitbox, the 15% hit will take precedence over the 19%. This adds to the critical spacing needed to connect with this move. In a real match, usmash isn't something that you can spam, so it takes very precise setups to go about hitting with this otherwise godly power hit. Since this is essentially the only uber-powerful move Peach has, we might as well share our knowledge on how to hit with it when possible.
Shield breaks: Virtually any character can be sweetspotted with usmash on a shield break if you time it right. The timing and positioning of Peach varies due to constantly moving body of your shield broken opponent, and often involves very specific timing (practice, practice). Kirby, Pikachu (but not Pichu), and Jigglypuff cannot be hit from a shield broken state, they are too short. Being directly below them on a sloped surface is the only way to connect with it.
How do you shield break? Skillful use of Mr. Saturn, or death turnips. Hey, it's more than what other people get, and if you do break their shield, you get a chance to really punish a la Fox.
Team Play: When your teammate has caught someone in a grab, it's also easy to shoulderpad the grabbed enemy. Position yourself so that the enemy is in between you and your teammate, and usmash. More often than not you'll get a shoulderpad out of it. Again, practice and see. Fox and Peach are quite deadly this way, both being capable of usmash killing when either one gets a grab.
http://www.youtube.com/watch?v=qbAOsQo4aKY <-example here
*Several dash attacks can also be punished by usmash when shielded. They're already running into you so half the setup is done. Prime examples of who can fall to this are Jigglypuff, Peach, Zelda, Samus, and more that I can't confirm at the moment. Be aware that you need at least 13 frames of advantage for this to work, assuming your timing is perfect.
Many characters can also be hit if you chase their rolls perfectly. Any type of roll can be punished. A tech roll, ledge roll, etc. This works when they manage to roll into you, but not past you. More oten than not they'll wind up into the shoulderpad.
If your opponent DIs your dthrow incorrectly (towards you instead of away) and you usmash in response, the sweet spot is capable of connecting. Like against Roy, Ganon, Sheik or others with similar fall speeds. They need about 100ish damage racked up first.
From dtilts with no DI
The 3 fast fallers fall so quickly that, after being dtilted at certain damage levels, they'll fall right into the usmash sweetspot without being able to escape. You can charge it up, and if you release it at the right time, it will sweet spot and KILL. However, they need to not DI the dtilt.
Fox: starting at 70 and up to 85 (roughly), connecting with a dtilt that isn't DI'd will pop Fox up into the air and fall, and leave him stunned enough so that he falls right into the usmash sweet spot (you may have to dash over a bit first). These two moves wind up doing about 32-34 damage, and gets vertical KOs below 110%.
Falco: add about 3 damage to Fox's figures.
Falcon: Works from a little under 80 to slightly 90, I can best gather.
There are several other numbers on characters where you can dtilt-usmash, but I'm too lazy to figure them out. They're all low figures, so they won't lead to kills.
Jiggs: both her dash attack and her Pound leave her vulnerable to usmash when you shield it. dash attack almost assuredly leaves the puff getting sweetspotted, while the Pound is dependent on her position.
If Jigglypuff misses a Rest, you cannot normally punish her with a shoulder pad. However, if she is on a significant slope (the ones on DK64 are enough), you can get under her and hit with it when you turn your back. Push her a little to the slope if you have to.
Ganondorf: Works when Ganondorf misses his ground Down+B and you're inside him.
Sheik: You can punish her Vanish lag with this! http://www.youtube.com/watch?v=CDcBFA5beMI
However, it is much harder than the vid makes it appear.
1. You must be right next to her, with back-turned for the sweetspot to hit.
2. The usmash must connect 25-29 frames after Sheik lands. Too soon and it won't sweetspot. Too late, and Sheik can act.
3. Pivoting an usmash is not easy on the fly.
I'm not quite done, but help me out here, guys.