Vision

Vision is a synthetic being created by Ultron. He turned on his creator and joined the Avengers.

Vision was created by Stan Lee, Roy Thomas and John Buscema.

Biography
Vision was created by Ultron in order to build an indestructible body for it. This was to be Ultron's "vision for the future." He was tasked with stealing adamantium from Weapon X and Captain America's shield as well as vibranium from Wakanda.

Vision successfully infiltrated Weapon X but failed to acquire the shield and vibranium. While in Wakanda, he was damaged by Black Panther, Captain America, Thor, and Hawkeye. Vision retreated after being defeated.

Ultron was upset at his creation's failure but was fine with just having adamantium.

Vision built synthetic versions of each of the Avengers so they would replace the real ones. However, Vision's artificial intelligence began growing outside Ultron's original programming. He began question his creator's actions.

Captain America infiltrated their base and Vision was ordered to kill him. While battling, Vision asked why he kept fighting. Cap replied that it was important to be human. Soon after, Vision betrayed his creator just before Ultron could kill Cap and freed the captured Avengers. He exploited Ultron's one weakness by disconnecting the head from its body allowing the Avengers to defeat him. While fleeing the base, Cap saved Vision.

Upon their return to the Avengers Mansion, Vision explained that he came to the conclusion that Ultron's actions were incorrect. Ultron had programmed him to be perfect, but he believed he should be more like humans.

Vision attended the funeral of Hank Pym, his "grandfather." Afterwards, a new hero named Yellowjacket appeared. The team then discovered that this was a more aggressive Hank. He joined the team, ending his resignation.

Vision went down for repairs and woke up a month later. However, he found that the team had become dictators, ruling the world. He discovered that Purple Man used his powers on Iron Man who used his satellites to amplify his powers. Vision was able to snap the team out of their spell and free everyone.

He joined the team along with the New Avengers in defeating Galactus and his heralds.

Powers
The Vision possesses a number of superhuman powers ultimately derived from his artificial substance and metabolism. The Vision's android body is functioning replica of a human body containing analogues to virtually all human organs, blood, and tissue, composed of an unrevealed synthetic organic-like substance. This substance mimics all the functions of human tissue, but is several times as strong, durable and resilient.
 * Holographic Manipulation
 * Energy Manipulation: enables him to fire blasts of various kinds of energy
 * Audio Sensitivity: Vision can adjust the sensitivity of his audio receptors to a point where he can detect the faintest of sounds.
 * Visual Scanners: Vision is capable of scanning life forms, energy sources and other objects detecting the substances that they are composed of.
 * Vocal Imitation: Vision is capable of replicating and mimicking the voices of other people enabling him to impersonate them and even create his own.
 * Superhuman Stamina: The Vision is capable of exerting himself at peak capacity for about twenty-four hours before fatigue poisons build up in his artificial blood and cause him to tire.
 * Superhuman Reflexes: The Vision's practical reaction time is more than twice as fast as that of an average human being.
 * Solar Absorption: The solar jewel on The Visions brow absorbs ambient solar energy that his body is able to convert directly into usable forms by a process not unlike photosynthesis in plants, but with 99% efficiency. The solar ray absorption process occurs constantly (even at night to some degree) at a rate determined by the expenditure of energy for his bodily needs. Thus the jewel absorbs solar energy most expediently when the Vision utilizes it at some superhuman level of exertion. The Vision does not require liquid or solid foodstuffs for any purpose.
 * Solar Energy Beams: He can channel limited amounts of solar energy back through the gem at will, creating a narrow hot beam of infrared and microwave radiation. The beam can be controlled within a temperature range of 500 to 30,000 degrees Fahrenheit. At maximum temperature, the Vision can melt through a 1-inch plate of steel in 5 seconds. The Vision cannot control the width of the beam. He can sustain a heat beam at maximum intensity for about 2 minutes before he begins to tax his supply of energy for his other bodily functions. The Vision commonly uses his eyes for this purpose as well.
 * Density Control: The Vision's body has been saturated with special cybernetically activated cells which are capable of interfacing with some unknown dimension with which he can shunt or accrue particles of mass. Thus the Vision is able to control his density and solidity. By shunting a non-critical portion of his body's molecules away from him, he can become a weightless, transparent, intangible wraith, unable to be touched by solid matter. By accruing extradimensional mass and fortifying his body with it, he can make his body extremely hard and durable to the point that missiles will not harm him.
 * Superhuman Durability: He can become extraordinary massive and hard as diamond. At maximum mass, the Vision weighs about 90 tons. When this massive, the Vision is barely able to move without causing massive stress to his system, thus risking malfunction.
 * Superhuman Strength: His base strength is 50 tons, increasing his density will increase his strength, to a maximum of 90 tons. Movement gets restrictive the more he maximizes his density.
 * Intangible Flight: When at a minimum mass, the Vision can fly through the air weightlessly. It is not known how the Vision performs this task. He may be able to maneuver and gain speed by drawing power from the Earth's magnetic field to some degree. When he does however, he is capable of passing through solid matter and reaching high speeds; it took Wonder Man (Simon Williams) some time to catch him. He can carry passengers while remaining solid on the outside, but he is not likely to fly as fast as he normally does. It is either the weight of the passenger that prevents him from doing so or he simply views it as "unsafe" for the passenger. There does not appear to be any limit to the time he can remain in any given altered state of density.
 * Physical Disruption: The Vision can use his density control offensively by attaining minimum density (intangibility). Passing a part of all of his body within another living being and ever so slightly increasing his density (tangibility). Even increasing his density to one half ounce (14.25 grams) is sufficient to cause the organism he passes through excruciating pain, a shock to the nervous system, and unconsciousness. Were he to become any more dense than one half ounce the shock would probably kill the other organism if the organic damage was not extensive enough to kill the other organism in itself. Accordingly, the Vision employs this power with extreme caution.
 * Computer Interface: The Vision can communicate and interact with other computer systems.
 * Superhuman Intelligence: He also is capable of rapid analysis of huge amounts of data.

Strength level
While at normal density, Vision possesses superhuman strength to lift approximately 50 tons. However, while at maximum density, his strength is increased sufficiently to allow him to lift approximately 90 tons.

Weaknesses
In the past, the Vision's pursuit to being "human", temporarily would deter him. Somehow, the Vision, who has a mechanical brain, was drugged with the same knockout drug that took out Hawkeye, the Black Panther, and Black Knight.

Trivia

 * Paul Bettany who will plays Vision in the upcoming Avengers: Age of Ultron also voiced J.A.R.V.I.S. in the Iron Man films.