Kamehameha

Kamehameha is 's and Super Saiyan Goku's standard special move in Super Smash Flash 2. The move involves Goku (and under Kaiō-ken) or Super Saiyan Goku concentrate their Ki into a single point between their hands and then thrusts forward to shoot out a powerful streaming beam of ki. It is also Goku's signature move in both the manga and anime.

Overview
The Kamehameha is formed when cupped hands are drawn close to Goku's side and the ki is concentrated into a single point between the cupped hands (and the hands must be really close). The hands are then thrust forward to shoot out a streaming, powerful beam of energy. This attack has limited range, and decreases in power as it gains distance. Kamehameha goes through four initial stages (flashing and growing in size once every second: after the third stage it takes two seconds to reach the highest range) over approximately 5 seconds; then it maintains a constant size (and the range cannot be increased after reaching this point) but glows brighter, with the interior flashing. This is full charge. It is possible to release Kamehameha at any charge by releasing the special button. Similar to the Falcon Punch, Goku has the ability to turn around while charging the move.

Kaiō-ken Kamehameha
When used by Kaiō-ken Goku, it is called the Kaiō-ken Kamehameha (界王拳・かめはめ波; World King Fist Turtle Devastation Wave). This attack is much faster and has better range but is weaker and cannot be fully charged unless the player immediately charges the attack once using Kaiō-ken, and releases it as soon as it is finished charging.

Super Kamehameha
When Super Saiyan Goku uses Kamehameha, it is called the Super Kamehameha (超かめはめ波, Chō Kamehameha) and is much more powerful and has a longer range. While charging up a Kamehameha in midair it will slow your descent. When Super Saiyan Goku releases a fully charged Super Kamehameha, the attack becomes known as the True Kamehameha (本場のかめはめ波, Honba no Kamehameha), turning into his SSJ3 form and releasing a giant wave of energy.

Origin
The Kamehameha is the first Ki-based attack introduced in the Dragon Ball franchise and continues to be the most commonly used, not only due to being iconic but also simple and practical. Goku's martial arts teacher, Master Roshi, is the first person on Earth to discover it, and it had allegedly taken him fifty years to develop. Goku was not taught it directly, but first learns it upon seeing Master Roshi perform it once in order to put out the fire on a burning mountain (though destroying the mountain entirely in the process).

Even in the earliest points of the series, long before large-scale destruction was a common occurrence, its destructive power and reach were supernatural in magnitude. Along with destroying the aforementioned mountain, it was also used to destroy Earth's moon to stop Goku, rampaging as a great ape, from destroying the World Tournament.

Being such a common attack, it was natural for variations to spring up as the series went on. Out of the variants that appear in SSF2, the Super Kamehameha is first used against Piccolo, the Kaiō-Ken Kamehameha was used notably against Vegeta and Frieza, and the True Kamehameha was used against Majin Buu. All variants tend to appear as separate attacks from each other in the video game adaptations.

Trivia

 * In its first appearance in v0.7, the fully-charged Kamehameha was the single most damaging attack—barring final smashes—in any version of SSF2, dealing 51% damage. Its power was significantly reduced in later versions.
 * The Kaiō-Ken Kamehameha went through a number of drastic changes between versions. In v0.8a, Goku skipped the charge entirely, instead immediately releasing a Stage 3 Kamehameha. In v0.8b, the charging returned, but it was impossible to fully charge; the Kaiō-Ken would run out an instant after Stage 3 began, interrupting it.