General boss guide
Pikmin bosses are harder versions of enemies that usually appear after you get a new pikmin. In pikmin 1 a good stategy to handle them is the red pikmin, just throw them on the boss and whistle them in when the boss is going to attack you. In pikmin 2 spam throw purple pikmin at them make sure to whistle them back before the boss kills them, (because purple pikmin are very valuble and you will need alot of them if you plan on getting all the treasures.), and in Pikmin 3 you should usually break armour if the boss has it or stun the boss, then charge at it to inflict damage. Also, if you just started a boss fight and you have no idea how it works then you should probably look around for a weakness that a new pikmin you recently found can exploit.