"Smash Moveset for Rainbow Dash"
By NudeBeach (https://pastebin.com/u/NudeBeach)

URL: https://pastebin.com/qEWb4qGM
Created on: Tuesday 14th of January 2020 10:42:44 PM CDT
Retrieved on: Saturday 31 of October 2020 03:55:09 PM UTC


Up+B: Flight - Rainbow Dash takes to the air with her wings, flying freely at a reasonably-high speed for several seconds. The player can use any of her air normals without penalty during this time. She leaves a small rainbow trail behind herself during this move, and if she flies into the trail she's already left behind by going in a circle, she'll repeat the path several times at a high speed, creating a tornado that deals high damage and knockback, but doesn't move from the spot it was created in, and renders her instantly helpless afterwards.

Neutral B: Dashing with Rainbows - She swiftly lunges in the direction she's currently heading (or straight forward if used while standing still). This goes through enemies but not projectiles or solid objects. If Rainbow Dash is hit by a melee attack during this, neither the knockback nor the damage of that attack happens, and Dash speeds up, instantly moving to the end of the move's distance, and damaging any enemy between her and that spot in a flash of rainbow colors while flinging them a set distance behind her. After the move ends, she needs a moment to recover - on the ground, she'll skid with her hooves, in the air, she'll flutter her wings to brake. If she damages an enemy with this move, she needs very slightly more time to recover.

Side+B: Roughhorse - Rainbow Dash pauses with a sparkle effect, then does a tackle with her forelegs outstretched in any direction (via directional input from the player). If she hits the enemy, she'll tumble with them for a moment before flying up and slamming them into the ground (if RD connects with the enemy on the ground), or pummel them with her forehooves before turning around and bucking them away (in the air). Either variant does good damage, but only modest knockback. This goes through projectiles, but Dash needs a moment to recover on a miss.

Down+B: Weather Control - Dash kicks a small ball of cloud forward, and it travels a modest distance before swiftly growing into a two-character-sized stormcloud. This stormcloud lingers for a short while, periodically electrifying itself, which deals damage to anyone touching it, or particularly close to it. It can be destroyed via attacks, though it has a small amount of HP which must be depleted to do so. The cloud stops projectiles while electrified, but is not a solid object.

Final Smash: Sonic Rainboom - Rainbow Dash flies up offscreen before flying back down to the spot she left from at a high speed - then abruptly changing course back upwards when he hits that spot, instantly doubling her speed and setting off a large, powerful explosion of rainbow light. This explosion consists of three concentric rings of rainbow, which deal high damage and knockback to enemies on contact, but can be dodged through, one-by-one with good timing. The rings spawn on semi-random frames, so the dodge can't be totally memorized. After the move ends, Dash falls, in helplessness, to the spot she started the move from.
 


Rainbow Dash, rather obviously, has high speed with multiple movement options, and is at her best in the air. Her dashing attacks can go in more directions if she has less solid surface around her, and her stormcloud attack likewise has more of its hitbox exposed if spawned in midair. She doesn't have much in the way of KO moves besides her smashes, final smash, and the tornado from her Up+B attack, which is hard to use effectively. 
Between Dash's moving counterattack, ability to ignore multiple kinds of attacks, and tendency to pause or become helpless once one of her specials is finished, using her recklessly is just as dangerous as attacking her recklessly.