PK Thunder

PK Thunder (PK, PK Sandaa) is the Up Special Move for Ness and Lucas. When used, it creates a bolt of lightning whose direction can be controlled using the control stick. As such, using PK Thunder will result in Ness and Lucas not being able to move or defend, because the control stick is used to aim PK Thunder. If either PK Thunder hits an obstacle, it will disappear.

Ness
The head of Ness' PK Thunder does 8% damage and hits once, then disappears. The tail of Ness' PK Thunder is longer, and deals more stun/damage than the tail of Lucas'. Ness' PK Thunder is also considerably faster. When Ness hits an opponent with the PK Thunder's head, the enemy is knocked back towards the direction it was coming from.

Lucas
Lucas' PK Thunder does 9-10% damage, goes through enemies, is slower, and can score multiple hits. The tail of Lucas' PK Thunder is shorter, and deals less stun/damage than the tail of Ness'. Lucas' PK Thunder turns in a tighter circle than Ness', meaning that it is easier to control, and can be used to recover in narrower spaces. When Lucas hits an opponent with the PK Thunder's head, the enemy is pushed away.

Uses
Since Lucas' PK Thunder does not disappear after hitting an opponent, it can chase the enemy around the stage. It is a useful edgeguarding tool because, unlike Ness' PK Thunder, Lucas' PK Thunder's head will push the enemy away from (instead of towards) the point of impact. The tail for both characters' PK Thunder has transcendent priority and cannot be cancelled, and can also break Smash Balls, making it useful to acquire a Final Smash if the Smash Ball is far away.

In addition, both sides of the head have more priority than the front and they have a direction of knockback perpendicular to the direction the Thunder is moving. The sides can hit a shield safely without the thunder disappearing, and due to hitbox renewal (the head can only hit once every 48 frames) it is possible for the thunder to go through shields.

On the other hand, Ness' is more useful for techniques like juggling, since after his Thunder hits an enemy, he can use it again repeatedly. Also, as it pulls opponents towards him, it can keep opponents with a good aerial game from staying in the air too long. After both characters pull this move in the air, they are sent in a helpless fall animation.

PK Thunder Barrier
In Melee, the uncontrolled thunder can hit anybody, not just Ness' opponents. This means that one can actually use the PK Thunder as a barrier, using the tail to intentionally block oneself from flying off the screen after being hit. This is called a PK Thunder Barrier.

PK Thunder 2
"PK Thunder 2" or "PK Rocket" is the term used for hitting Ness or Lucas with their own PK Thunder while it is still under their control. The Japanese developers called this move PK Jibaku (PK). The word jibaku means 'self-destruct' or 'suicide bomb', a fitting term for a tactic that turns Ness and Lucas into human missiles.

By using this technique, they will transform into a human projectile, which will move in different directions depending on what part of the body is hit. This is also Ness and Lucas' main method of recovery, given that it launches them fairly far in a straight direction. In addition, while performing PK Thunder 2, Ness' PK Thunder curves in a larger arch than Lucas, thus Lucas requires less room to use PK Thunder 2 than Ness. However, Ness' PK Thunder is faster, making up for this. While using the move, the user will fall much slower. Unfortunately, using this in a trench makes it more difficult (to flat-out impossible) to guide the PK Thunder without striking the walls of the trench. It should also be noted that on stages like Battlefield or Final Destination, if Lucas' PK Thunder 2 is aimed wrong, the user will bounce right off the corner of the stage, leaving him in a helpless animation away from the ledge.

Ness
Ness' version deals one strong blow, dealing 25% damage with extremely high knockback, KOing lighter characters at 30% or less, although the Super Smash Bros. version is considerably stronger than the Melee equivalent. Also, if used up close, it can bring Ness to a short stop.

Lucas
Lucas' version of the attack hits multiple times, and if all hits connect, it will deal a massive 43% damage and has decent knockback, making it Lucas' most damage-dealing move, with the exception of PK Starstorm, which may not be used in competitive play. However, it is unlikely to get the full 43%, as it takes very long to start, and as such, is easily dodged or DI'd out of. Lucas' PK Thunder 2 covers more ground than Ness', so Lucas' is slightly more effective.

CPUs
CPUs playing as either Ness or Lucas are also programmed to use this strategy, but they only use PK Thunder 2 vertically, even in situations where only recovering horizontally or diagonally would prevent death.

Thunderglide
For tactical uses, Lucas' PK Thunder 2 can be used to "Thunderglide". Thundergliding is when the player runs off a platform, then immediately uses PK Thunder. The effect should come out to being the PK Thunder being much closer to Lucas than normal. Then, guide the thunder into Lucas and he should angle down towards the ground. If performed right, Lucas' direction will go from diagonal to horizontal as he glides along the ground. Otherwise, he'll crash into the ground like a normal poorly aimed thunder. Lucas will stop at the edge on his own, making this move safe to use on a stage like Battlefield. The thunderglide is great for surprising opponents for a quick 20-43% damage.

Origin
This move is based on a psychic attack of the same name in the Earthbound universe. Unlike the Super Smash Bros. series, in Earthbound, PK Thunder can attack multiple enemies at once, but loses accuracy as there are fewer enemies. In Mother, PK Thunder had 100% accuracy and the final stage can hit all opponents. In Mother 3, PK Thunder could miss, but the accuracy was much better than in Earthbound, making Mother 3's PK Thunder much more viable than Earthbound's PK Thunder. Like Ness' and Lucas' other special moves, they don't learn the attack in their games, Earthbound and MOTHER 3 respectively. Paula and Poo use it in Earthbound, while Kumatora uses it in MOTHER 3.

Trivia

 * In the official Super Smash Bros. Brawl Prima strategy guide, it is incorrectly stated that Lucas' PK Thunder hit opponents once, and sends them flying, while Ness' PK Thunder, on the other hand, is able to hit opponents multiple times.
 * The speed of the PK Thunder is not affected by a timer.
 * In Melee, only a level 9 Ness CPU will use PK Thunder to recover. Level 8 and below will never use PK Thunder to recover.
 * In Melee, if Ness aims the PK Thunder 2 downwards causing him to hit the ground, the electricity is still surrounding him.