Master Hand

Master Hand is a mutation of Mario's left hand that appeared in Have you seen this polygon? and made a cameo appearance in Flashbacks. After losing his left hand and blasting to Final Destination, Mario realizes that he has to defeat Master Hand in order to regain the appendage. It appears that Master Hand is still sentient after being reattached to Mario's body.

Master Hand's main attacks are smashing, handguns, walking, farting, and saying bad things. It seems his favorite food is ultra peppers.

Master Hand reappears in Retarded64: Stupid Smash Bros, where he is the main antagonist. Master Hand constantly demands Mario the Smash Ball that he lost and got stolen from him. Mario disobeys the hand, causing him to send fighters and mind control people from the Mushroom Kingdom to fight Mario until he gives up the Smash Ball, however, all of them are retarded and too stupid and useless to even fight. This causes Master Hand to go crazy to the point he does the entire thing for himself, weakening Mario, but is even defeated by Ganondorf, in his Beast form, to charge after him and knock him offscreen.

Master Hand reappears again in SMG4: Mario Battle Royale, as Game Master. He also tells Mario some of the rules.

He reappears in The Smash 5 Trials.

In The New Smash Bros, Master Hand gets Arthritis so Crazy Hand takes Smash Bros. He however gets better during the Adventure mode and takes back Smash Bros. He then appears in Vs. Master Hand mode with multiple firearms because he's still sick, leading to Mario committing suicide.

He is technically responsible for the events in SMG4: Mario And The T-Pose Virus.