Focus Attack

Focus Attack (, Saving Attack) is Ryu and Ken's down special.

Overview
When the special button is held, the user will emanate a black aura and begin charging up a powerful attack. After about one second, or when the button is released, the user throws out a concentrated black ink-trailed punch (Ryu) or kick (Ken) that deals 12% damage uncharged, 10% partially charged, and 17% fully charged (Smash 4); a fully charged hit is unblockable and causes opponents to crumple to the ground slowly, leaving them open for a followup attack. A fully-charged Focus Attack connecting with an opponent in the air will simply paralyze them for a few moments, although the duration is still moderately long. A semi-charged Focus Attack can still crumple opponents (albeit for a shorter time), while an uncharged Focus Attack only deals low damage and knockback, and will not stun. If Focus Attack connects with an opponent who is already crumpling (e.g. from Skewer or a previous Focus Attack), the move will only deal knockback even if fully charged. However, this can potentially set up combos. The direction of this attack can be changed by holding left or right after the special button is pressed, although the amount of damage done is not increased if the direction is changed, unlike moves such as the Falcon Punch.

In Smash 4, Ryu gains a unique form of damage-based armor when charging this move that can resist a single hit before they affect them as normal up to a given percentage. This ranges from 22% to 39%, accumulating by a set amount every frame until it reaches the maximum range. This can let the user resist attacks that would usually be devastating (such as shrugging off Ganondorf's Warlock Punch in Ryu's intro video for Smash 4). This only works for one attack however, so multi-hit attacks and grabs are an effective counter to this move. Despite the cap being extremely high, the move's armor cannot withstand immensely powerful attacks such as some Final Smashes or the Dragoon, making it useless for negating them. However, Ryu gains a high amount of knockback resistance to attacks while charging, which can let them survive at low percents if hit by them.

In Ultimate, the damage-based armor was severely nerfed, now with a range of 14-28%, accumulating by 0.24% per frame and being active from frames 1-20 (though it can still be extended). Ken's Focus Attack is 1 frame longer than Ryu's, having 11 frames of startup rather than Ryu's 10 frames. The frame data and armor for both characters is identical, however.

In Ultimate, Ryu and Ken are able to cancel into Focus Attack on hit by connecting any of their special cancelable attacks and inputting Down Special within the specific move's special cancel window.

The moves they are able to cancel are Tapped Neutral Attack 1 & 2, Held Close Neutal Attack, Tapped Close Forward Tilt, Tapped and Held Up Tilt, Tapped and Held Down Tilt, Down Smash, and all 5 of their aerials, including both hits of Ryu's Up Aerial.

Ken also says "There you go!" when using the move, unlike Ryu, who simply grunts.

Focus Attack Dash Cancel
Focus Attack can be cancelled by tapping left or right twice while holding down the button, making the user move a short distance in the direction pressed. This is known as a Focus Attack Dash Cancel (, Saving Cancel), often abbreviated as FADC. When the move is cancelled, it will be noted by a flashing star similar to those made by fast falling fighters. As such, a player can use the move's starting armor to plow through attacks or projectiles, then cancel it immediately for a follow-up; this is especially useful on laggy attacks.

The dash cancel can be used before the strike occurs or when the attack hits (including if it is blocked). If the strike is released, but fails to connect, the dash cancel cannot be used. Dash cancelling the Focus Attack even works in mid-air, giving the user a unique air dashing ability that improves his aerial maneuverability and adds to his recovery options.

Cancelling the Focus Attack right as the opponent gets hit is a reliable way to start combos. For example, at full charge if Ryu cancels backwards, it guarantees a sweetspotted forward smash that can be charged a small bit. If the player cancels forward, an inputted Shoryuken can be performed instead. However, a forward smash deals more damage than a Shoryuken, making it much more effective when racking up damage.

Canceling
Both Ryu and Ken can perform a Focus Attack out of some normal attacks due to their special move canceling mechanic. By pressing the special button after connecting with a normal attack, Ryu and Ken will cancel the endlag of the normal attack and perform a Focus Attack. The normal attacks that can be canceled include the first two hits of neutral attack, tapped and held down-tilt, tapped up-tilt, and proximity forward-tilt and held neutral attack (in Ultimate), to name a few. This allows them to deal extra damage in combos, improving their punish game.

Customization
Special Move customization was added in Super Smash Bros. 4. These are the variations:

Like the other DLC characters in Smash 4, Ryu has no custom move variations.
 * 1) Focus Attack: Default

Origin
This attack originates from the  series. Every fighter has access to a move called Focus Attack that can absorb one hit during its charging animation, but has slow startup otherwise. It is performed by pressing both medium punch and medium kick at the same time. The Focus Attack can be charged, and there are three stages to the move, each dealing more damage than the last; the level 1 (or uncharged) Focus Attack has the fastest startup, but causes little hitstun or blockstun, the level 2 Focus Attack can crumple the opponent for nearly 2 seconds if it hits and has decent blockstun, and the level 3 (or fully charged) Focus Attack is unblockable, possesses the super armor property until the hitbox becomes active, and crumples the opponent for a slightly longer period of time. The super armor can be disrupted by grabs, multi-hitting moves, and attacks that are classified as armor breakers, such as Tatsumaki Senpukyaku. Characters may dash out in either direction during the charging animation and when the attack hits. The Focus Attack, at the cost of two EX bars of the super meter, can also cancel the recovery frames of most moves on hit or block (or sometimes regardless of hit or whiff, particularly on projectile moves), which, in conjunction with a dash immediately after, can allow for extra combo opportunities or add an extra layer of safety when using a laggy move; this is known as the Focus Attack Dash Cancel (FADC).

Ryu and Ken use the exact same attack animation from the SFIV series in Smash Bros., complete with the black "aura" and ink effect around Ryu's fist and Ken's leg when they release the attack. However, in Smash, the move cannot be used to cancel other special moves or smash attacks, and the Focus Attack itself must either connect with an opponent or be slightly charged before it can be dash canceled, unlike in SFIV where the user is capable of dashing out almost immediately; however, Ryu and Ken can turn around right after the charge animation to attack in the other direction, an alteration unique to the Super Smash Bros. series.

Trivia

 * The animation of each fighter slowly crumpling to the ground after getting hit by Focus Attack is the same animation they use for being defeated in Stamina Mode if they are standing still and hit with a weak attack. It is one five attacks in the series that is able to force fighters into this animation, along with 's sweetspotted Skewer and three of Kazuya's moves (9th hit of 10-Hit Combo, Demon God Fist, and sweetspotted Devil Fist).
 * Super Smash Bros. Ultimate marks the first time outside of the main Street Fighter series that the Focus Attack can be used by more than one character.
 * Its other appearances were in Marvel vs. Capcom 3: Fate of Two Worlds (and the updated Ultimate Marvel vs. Capcom 3) and Tekken 7, where in both games, similarly to Smash 4, it was exclusive to one character.
 * Oddly, in Super Smash Bros. 4, a fully charged Focus Attack has shield damage coded, namely, 30, but this is never seen, as a fully charged Focus Attack is unblockable, meaning it won't hit a shield anyway.
 * In Super Smash Bros. Ultimate, if the Fixed Damage modifier is enabled in Training Mode, the opponent will crumple much more quickly.
 * Also in Ultimate's Training Mode, the combo meter will increase if the Focus Attack is repeated consecutively on a CPU with 999% damage, despite connecting more than one Focus Attack not being a true combo.