Master Hand

Master Hand is a boss in all 4 Smash games.

In Super Smash Bros.
Master Hand is the final boss in 1P Mode. He is fought on Final Destination

In Super Smash Bros. Melee
Master Hand is once again the final boss of Classic Mode, now joined by Crazy Hand.

In Super Smash Bros. Brawl
Master Hand is the final boss once more. He is also the boss of The Subspace Emissary

In Super Smash Bros. 4
Master Hand has the same role, however, on a high difficulty, once he takes enough damage, he becomes Master Core.