Simon Williams inherited his father's industrial munitions plant after his father died and his older brother, Eric, did not want to take over. Although a capable scientist, Simon nevertheless was not a businessman, and the company started to fail. Eric suggested that Simon embezzle money to invest in Eric's own business, which happened to be illegal racketeering with Maggia ties. The embezzlement and racketeering was discovered, and Simon went to jail, blaming his downfall on Tony Stark (a.k.a. the hero Iron Man and member of the team Avengers.)
Simon was released with help from the original Baron Zemo and his Masters of Evil. Simon agreed to undergo an experiment to give him superhuman powers, and Zemo gave him the costumed guise of Wonder Man, warning Simon that he would die without further treatments from Zemo in order to ensure his loyalty. At Zemo's behest, Simon befriended Avengers, pretending to be their ally, and lured them into a trap. However, he repented at the last minute and saved the Avengers from the Masters, seemingly at the cost of his own life.
In fact, Simon had really fell into a death-like coma. Before he was buried, his brain patterns were recorded for scientific purposes (and were later used to build the android Vision.)
Simon's body was about to be buried when it was captured by his brother, now known as the Grim Reaper and who had already battled the Avengers, blaming them for Simon's death. The Reaper wanted to use the body to bribe the robotic Vision to accept a human body. The Vision refused, where it was first revealed that Vision's mind was based on Simon's own brain patterns.
Eric later tried to have Simon's body resurrected by the voodoo of the Black Talon, and Wonder Man was used as a zombie to attack the Avengers. Instead, Simon was restored to consciousness by the Living Laser who was holding the powerful Serpent Crown artifact. Afterwards, the Avengers accepted Wonder Man as a staunch ally and he was later elected to full-time membership. His presence was always a source of tension for the Vision, who felt insecure as Simon was the source of his “life.” At one point, Wonder Man and the Vision were placed on "trial" by the Grim Reaper to determine which of them was the "real" Simon Williams. Simon was accepted as the "real" brother by Eric, but Wonder Man subdued the Reaper to save the Avengers.
Simon's effectiveness as a fighter was limited by a lingering fear of death and chronic self-confidence problems. Despite his fears, he helped the Avengers fight major foes such as Ultron and Count Nefaria, and he ultimately overcame his fear of death to play a key role in Avengers' struggle with the supremely powerful Korvac. Soon after this, however, Simon left the Avengers to become an actor, although he would find much more success as a Hollywood stuntman. He would occasionally return to the Avengers to help them on an as-needed basis.
Simon was among the Avengers who founded their West Coast branch. Although he continued to struggle with fear of death and failure, he largely overcame fear of death with emotional support from Hank Pym and the Vision. He confessed feelings of inferiority to the Vision, who he began to regard affectionately as a twin brother of sorts. He further conquered feelings of shame and fear by publicly confessing his embezzlement of funds from Williams Innovations, an act long assumed by many to be the work of his criminal brother, Eric. Simon gained enhanced fame and growing confidence as a result of his public confession, which ultimately helped him land a starring role in a major motion picture, Arkon IV, becoming a genuine Hollywood celebrity.
Simon served with the Avengers West Coast throughout its existence. During this time, he furthered his acting career and becoming romantically involved with Alex Flores, a screenwriter. He opted not to stay at the Avengers' Compound, but instead lived in a Los Angeles apartment where he befriended many of his neighbors.
When the Vision had been reduced to an emotionless robot after the seeming destruction of his artificial mind, Simon refused to allow the Avengers to duplicate his brain patterns as part of their efforts to restore the android. The Scarlet Witch, the Vision's wife at the time, became bitterly estranged from Simon for his refusal, which actually stemmed from the fact that he held a long-time infatuation with her, and unconsciously wanted the Scarlet Witch for himself. He finally agreed to allow the duplication of his brain patterns after a distraught Scarlet Witch suffered a mental breakdown, but the Vision declined the offer since he had realized that duplicating Simon's brain patterns would not truly, fully restore his lost personality, but merely create a similar facsimile. Simon became very supportive and attentive to the Scarlet Witch as she recovered from her mental breakdown, and he even sought a romance, briefly dating her. However, the Witch ultimately rejected Simon, which led him to overcompensate by pursuing assorted starlets.
On a later adventure, Simon joined with the Avengers to stop the alien races of Kree and Shi'ar from dragging Earth into their war. The Shi'ar developed a massive "Nega-Bomb" to decimate the Kree empire, and Simon and the Vision tried to stop it. Instead they were caught in the explosion. Simon found his powers mutating, eroding his mental and physical stability (for instance, he later found that his strength fluctuated with his emotional state, increasing when he became angry.) He radiated so much ionic energy that he began altering those around him. His neighbors in his apartment developed superpowers of their own, forming a short-lived team called the Crazy Eight. Ultimately, Simon's instability led him to leave the Avengers. As he struggled through, he tried to kindle his romance with Alex Flores, proposing to her.
Eventually, Simon returned to rejoin the Avengers' West Coast branch, only to find it had disbanded in his absence. Simon was contacted by Iron Man to join his new team, Force Works. During Force Work's fist mission, however, Simon was killed when intercepting a bomb set by potential alien invaders.
Simon was accidentally mystically resurrected by the Scarlet Witch, who had issued a magical summons to anyone associated with the Avengers during her capture by the sorceress Morgan Le Fay. He continued to exist as disembodied energy after his death, bound to the earthly by his long-unrequited love for the Scarlet Witch. He seemed to have sacrificed his life yet again to save the Avengers from Morgan Le Fay, but he began periodically manifesting in the vicinity of the Scarlet Witch as a sort of ghostly energy wraith, appearing when she needed help or felt lonely. Never fully resurrected, Simon was stuck "in-between" as it were, and was used by his brother, who was also deceased at the time, to weaken the borders between life and death and create a Hell on Earth, with resurrected versions of deceased Avengers as his lieutenants. Simon was similarly mystically enslaved by the Grim Reaper and pitted against the Avengers, but Simon turned on the Reaper after escaping his control. The Scarlet Witch was finally able to bodily resurrect Simon by realizing her love for him. Simon, in turn, was able to bodily resurrect his brother, by realizing their love for each other.
Simon elected to stay at the Avengers mansion, exploring his relationship with the Scarlet Witch while serving alongside the team as a non-member. He tried to rebuild his brotherly relationship with the Vision, who remained largely aloof. Simon continued to struggle with feelings of guilt and inadequacy due to the many mistakes and misdeeds he committed during his time in California, and he briefly left the Avengers Mansion to make the rounds of his Hollywood friends and associates in an attempt to make peace with his past life and make amends for the various misdeeds he had committed. He learned his one-time fiancée, Alex Flores, had fallen in love with someone else and was happily married, and they parted on good terms. Simon was ultimately cleared of any wrongdoing regarding deaths he helped cause during his time in Los Angeles, and with his friend the Beast, he defeated and exposed crimelord Lotus after defeating her pawn, It, The Living Colossus. He finally resolved to put his troubled past behind him and established the Second Chances Foundation, a non-profit charitable enterprise devoted to helping people in need, managed by his old agent Neal Saroyan and funded by the proceeds from Simon's films, merchandise and endorsements.
Simon began dividing his time between the Avengers and the Second Chances Foundation, trying to maintain a long-distance relationship with the Scarlet Witch at the same time, despite the fact that the passion had gone out of their relationship. When Kang attempted to conquer Earth, he interned many of its citizens in large camps, including a captive Scarlet Witch. Similarly captured, Simon was placed in the same internment camp. Both had realized during their time apart that they were no longer in love with each other -- the two of them having come together more from passion, loneliness and a sense of obligation than true love. The couple amicably ended their relationship and the Scarlet Witch admitted she was still in love with Vision, though she did not expect to act on it since he had finally moved on. The Scarlet Witch helped Simon escape internment and eventually Kang was defeated by the Avengers, whereupon Simon returned to California and the Second Chances Foundation.