Crazy Hand

Super Smash Bros. Melee
The Crazy Hand is the main villain in Super Smash Bros. Melee along with the Master Hand and Giga Bowser, and it is also the Master Hand's double. The Crazy Hand will appear when the player completes Classic Mode on normal, hard or very hard under 10 minutes and does not use a continue. The Crazy Hand is much more twitchy and sinister sounding than its right handed counterpart, and it also has more attacks and is covered in electricity. Crazy Hand more dangerous foe since it attacks more frequently, giving fewer opportunities to hit, which is more difficult in Classic Mode because the fight with him and Master Hand is timed. In addition, Crazy Hand is also fought in the 50th event match.

Super Smash Bros. Brawl
In Super Smash Bros. Brawl, he appears as a boss of the Subspace Emissary (See YouTube: SSBB - All bosses. Crazy Hand can be seen from 2:54 to 3:05 and Master from 3:43 to 4:00, distinguished by their mirrored thumbs.)

Interestingly, the Crazy Hand's trophy(Melee) (gained after beating Adventure Mode on hard or very hard) says that it embodies a being who wants to destroy (whereas the Master Hand's trophy says it embodies a being who wants to create).

Trivia

 * In Kirby and the Amazing Mirror, Crazy Hand appears as a boss along with Master Hand. Once defeated, Kirby can eat him and become Smash Kirby (He can use all of Kirby's special attacks from Melee.)

Trophy Information
''Where the Master Hand loves to create, its alter ego is impulsive and destructive, consumed with that hollow feeling which comes from destroying one’s own creations. The Crazy Hand appears when a player clears obstacles quickly and the Master Hand’s power is low. You have only one chance to defeat the Crazy Hand.