Rage
Rage is a new mechanic in Super Smash Bros. 4, where a character's attacks will deal increased knockback as his or her damage rises. The effect is similar to Lucario's aura mechanic, though the damage dealt by attacks does not increase, and the increase in knockback is less significant. Rage begins to take effect past 35% damage, and maxes out at 150% damage. At maximum rage, attacks will deal 15% more knockback than normal. Rage is visually denoted by characters flashing red and smoke rising out of them when they reach 100%, and the effect grows more visually intense as damage rises farther until the aforementioned 150%, though rage starts applying long before the visual indicators appear; this visual effect making characters appear to be enraged is what led to the mechanic being nicknamed "rage" by the Smash community.
The Rage multiplier is 1 + [(p - 35)/115 * 0.15], where p is the damage percentage of the attacker (but no less than 35 and no greater than 150)[1]. Thus the minimum possible multiplier is 1 (no Rage effect) while the maximum possible multiplier is 1.15 (all knockback is increased by 15%). This multiplier is applied to the end of the knockback formula (as the variable r), alongside other conditional ratios such as the crouching penalty (x0.85), smash attack charge interruption bonus (x1.2), and grounded meteor smash penalty (x0.8). The first two multipliers are mutually exclusive to each other, as one cannot be crouching and charging a smash attack (even down smash) at the same time. This multiplier can also be directly applied to the base knockback and knockback scaling values of moves, resulting in the same effective knockback when calculated.
The obvious application of rage is that it allows players at higher damages to land KOs sooner than they would be able to otherwise, which can help aid a losing player staging a comeback. However, rage is not necessarily a comeback-friendly mechanic. It can be used by players with stock leads to potentially survive for longer, as the player with a lower stock and damage cannot use their finisher's as effectively. Furthermore, the increased knockback from rage can potentially prevent combos from working sooner than they normally would, especially in combos that involve setups from throws with high base knockback, thus preventing players with high damage percents to increase the damage percents on a lower-damaged player. Rage can potentially assist in combos that rely on stage-specific combos that rely on forcing opponents onto specific platforms, but these combos, even without rage, can be more difficult to perform than standard combos.
Generally, characters with higher weights, such as Bowser or Ganondorf, benefit the most from rage, as their greater survivability allows them to both experience rage longer and to a greater degree. Furthermore, most heavyweights are less reliant on combos compared to other characters, allowing for the greater use of increased knockback with little concern of it preventing vital combos. Conversely, characters that can rack up damage quickly without rage can lose out on several combos they can potentially perform when they start building rage, especially those that rely on grab setups, such as R.O.B.. Characters with light weights, such as Kirby, also do not strongly benefit from rage, as their lower survivability can shrink the window for which they can take advantage of rage.
Like stale-move negation, Rage is not present in single player modes such as Training mode, though the visual effects are still present. As such, its effects can only be tested in Versus modes.
This mechanic was originally discovered by the Japanese community at the launch of Smash 4 on the 3DS in September 14, 2014, and was referred to as the "Hot Hot Effect". Ayuha and Chibo worked together to make a tutorial video on it and bring the information to the western scene, where Chibo then named it the "Rage Effect".
