Acidwraith

The Acidwraith may be the ectoplasmic incarnation of a kind of psychic phenomenon. Its appearance is generally humanoid in shape, with the suggestion of a head, body, arms and legs, but without distinct characteristics, and with an acidic, translucent body. The Acidwraith's name is a combination of acid, given its acidic appearance, and wraith, which means ghost or phantom.

Strategy
When encountered, the beast falls from the sky and moves around on its stone 'rollers'. It will chase Olimar and any Pikmin nearby, with greater focus on crushing the active Captain. It is invincible to any Pikmin assault, even if petrified, except that of Purple Pikmin. When a Purple lands on or near the Waterwraith in a fashion that would stun any other beast, it turns a deep shade of purple not dissimilar to that of the Pikmin that cause this state to come about. This will instantly kill the purple pikmin though. Thankfully, a new Candypop Bud species, the Dual Bud will combine two Pikmin together for a limited time. Once the time expires, it wil split back into two Pikmin. You need to combine a Purple Pikmin and a Green Pikmin to kill this beast. Like this, it is vulnerable to Green Pikmin attacks (it will asphyxate any other pikmin that attempt to attack it). When the Wraith's health has been fully depleted, the rollers crumble and the Waterwraith will scoot all around the cave, dissolving any Pikmin it walks through. Attack with more purple-greens and then you can easily attack it with green Pikmin. When defeated, it will vanish into nothing, and you will be troubled no more.

Strangely, petrifying the Acidwraith makes it less vulnerable to Purple Pikmin, in which case the Pikmin must be thrown in a perfect arch for enough impact to make the creature susceptible to attack. In other words, Purples make a certain "squashing" sound when they hit an enemy or a plant; when this sound is performed, a creature may also be stunned. These effects can only occur when the Purples have a straight fall downward after their throw (the distance in which they fall vertically is irrelevant, as long as it exists). Finally, when all these circumstances are achieved, the Acidwraith may gain damage; this will not happen when Purples are thrown on it without the drop.

Petrification glitch
When the rollers fall, petrify its roller. When the Acidwraith itself lands, it too will be encased in stone, but the roller will revert to its normal state before the creature itself. Petrify it again, and the Wraith is normal, but not the rollers; the Wraith will have problems lifting them. Its audio will get messed up, as it cries with each attempt to pick up the front roller. The beast won't turn purple when Purple Pikmin are thrown at it. This is because it needs to lift its rollers first.

After Years
In the game, Pikmin:The After Years, this enemy will drop 2 random colored 20 pellets and 1 10 pellet.

-- Gamefreak75