M. Bison, known as Vega in Japan, is the supreme leader of the criminal syndicate Shadaloo. His ultimate ambition is to control the governments of the world, funding his operations through a vast network of illegal activities including drug trafficking, arms dealing, and terrorism. He is a classic megalomaniac driven by a lust for power and a desire to be seen as a god, showing no compassion or mercy towards anyone who opposes him or who he considers insignificant. He demands absolute loyalty from his subordinates, whom he views merely as pawns to be discarded once they have outlived their usefulness.

Personality-wise, Bison is supremely arrogant and narcissistic, believing himself to be the superior fighter due to his mastery of an inherently evil energy known as Psycho Power. To fully master this power, he expelled all the humanity and good from his soul, which later manifested as the character Rose. This act left him with a dark, irredeemable spirit that takes great pleasure in tormenting and exploiting others. While he has a twisted sense of humor and a characteristic "business before pleasure" attitude, his core nature is that of a ruthless and unforgiving dictator.

In the story, M. Bison serves as the final boss in several Street Fighter tournaments, which he often hosts to lure powerful fighters for his own ends. He is the object of revenge for many characters. Chun-Li seeks to avenge the death of her father, whom Bison personally killed. Guile is driven by the apparent death of his best friend Charlie Nash. T. Hawk wishes to avenge his homeland and father, which were destroyed by Shadaloo. Cammy, a genetically engineered clone created from Bison's own DNA, fights to break free from his control and discover her true identity. Bison also takes a particular interest in the warrior Ryu, believing his body to be a worthy vessel for his own soul when his current body begins to fail.

Throughout the series' timeline, Bison undergoes significant development regarding his physical state. In the Street Fighter Alpha series, his body begins to deteriorate under the strain of his own Psycho Power. He creates Cammy as a potential new body and seeks Ryu as another host. After a climactic battle, he is forced to inhabit Rose's body temporarily before his scientists can forge a new one for the events of Street Fighter II. This new body is considerably weaker, as his soul had been reunited with its good half, which diluted his power. He is later seemingly destroyed by the warrior Akuma. In Street Fighter IV, he returns in yet another new body, secretly manipulating events from behind the scenes. After his final defeat by Ryu in Street Fighter V, a remnant known as Phantom Bison continues to haunt his former creations.

M. Bison is a formidable fighter who wields Psycho Power, which allows him to perform a range of supernatural abilities. His signature techniques include the Psycho Crusher, where he wraps himself in Psycho Power and flies at his opponent, and the Double Knee Press. He is also capable of teleportation, creating after-images of himself, and projecting Psycho Power as a projectile. He can use his power to brainwash others and has repeatedly demonstrated the ability to transfer his soul into a new host body, making him extremely difficult to kill permanently.