Appearing early on in the Avengers comic series, the Scarlet Witch and the Vision share a common history: they were both introduced as villains. The Scarlet Witch, while teamed up with her brother, showed up for the first time under the control of their on-again/off-again father Magneto in his Brotherhood of Evil Mutants before both of them ultimately joined the Avengers. The Vision's story was even more complex, as he was a synthozoid body belonging to the original Human Torch, embedded with the consciousness of Wonder Man and given life by the baddie Ultron.
Later, The Vision and Scarlet Witch became as a couple primarily because they'd both only appeared in the Avengers comic. Unlike other Avengers, many of whom had their own ongoing solo series, this allowed their relationship to take center stage. The lack of outside elements that could have interfered with character arcs made the relationship convenient from an editorial perspective. Given this somewhat mechanical reasoning behind the two of them hooking up to begin with, it's not particularly surprising that they seemed like a couple of mismatched puzzle pieces from the start.
The couple was wed in Giant-Size Avengers #4 alongside an equally troubling marriage between sometimes-Avenger Mantis and a tree-alien in the form of her deceased lover, The Swordsman. After that, there was a mini-series from 1982 that ran for four issues, and a 1985 maxi-series that ran for twelve, both titled The Vision & The Scarlet Witch. Despite having different creative teams, they share many common themes—like Wanda's need for protection, The Vision's need to be viewed as human, and the two trying to build a normal life together.
At one point, the Vision and his “brother” Wonder Man encounter the villain known as the Grim Reaper. The Reaper views the Vision as a mockery of his brother while refusing to believe that Wonder Man is his real brother, as Wonder Man was revived from apparent death after his consciousness was kept within a computer for several years. The Reaper attacks them both, and the Vision and Wonder Man team up together to fight him. Ultimately, the Reaper apparently commits suicide, unable to live with the idea that the reincarnated Wonder Man might really be his brother.
As for the Scarlet Witch, it's more or less impossible to explain the heritage of Wanda and her brother Pietro. Even people dedicated to piecing together continuity have pretty much thrown their hands up in frustration on those two. A series of retcons has rendered their backstories illegible. During this era of continuity, the twins were the children of a Romani woman named Magda and the supervillain Magneto. Currently, the questions of Wanda and Pietro's lineage are more confusing than ever, but there are references to it.
In the first Vision & the Scarlet Witch mini-series, Golden Age hero the Whizzer shows up, believing himself to be the father of the twins. (Long story short: the Whizzer was a Golden Age Marvel superhero that gained the power of super speed from a blood transfusion with a mongoose.) Wanda chooses to continue pretending he is her father, despite believing it to be Magneto, because she sees him as a lonely old man who could use the comfort. She, he, and the Vision all go to help rescue his superpowered son Nuklon, who has been raised in a playpen in a lab into his adult years and is so powerful he melts the Vision's arm to slag within moments of their arrival. It's a very bizarre segue in the middle of a loosely plotted four-issue mini-series, but still important, as it gives us an early indication of Wanda's inclination toward keeping secrets or hiding the truth from herself and others. It also illustrates her unsettling but consistent willingness to put her husband's life in danger.
In the second series, most of the stories are likewise standalone. The couple has taken leave of the Avengers and are attempting to build a life together, despite general intolerance from neighbors who refuse to live in the same neighborhood as they do, calling them “unnatural.” In the comics of the time, these two characters were used as a stand-in for relationships that were difficult for the general public to accept—for instance, interracial or homosexual relationships. Thereby, Wanda and the Vision are shown in the second series attempting to live “normal” lives in the suburbs, away from the Avengers, and wind up being treated with hostility by their neighbors.
The problem with that approach to these characters is that the Vision and Scarlet Witch actually do have a really messed-up relationship. Unlike interracial or homosexual pairings, the scrutiny their partnership comes under is really quite valid. The metaphor fails because they're both superheroes, known for getting into huge fights in the middle of the city and causing untold amounts of property damage and accidental deaths. On a personal level, there is an uneasy element of coercion in most of Wanda's relationships, friendships included, but particularly where the Vision is concerned. In most stories of these two, the Vision goes to some lengths to become the husband she wishes he could be, only to shatter her concept of self when he inevitably reverts to form. Wanda's emotional frailty and the Vision's philosophical confusion are similar beasts. When they collide, the results are often disastrous.
After the second Vision and Scarlet Witch series, the two join the West Coast Avengers, a series that saw the Vision dismantled entirely, rebuilt as a truly emotionless robot. Wanda is forced to emotionally deal with a husband who is, for all intents and purposes, dead but still very present. He tells their children that he's not their father, which leads to the annulment of their marriage. Wanda's children are even, for a time, proven to be figments of her own imagination, which has catastrophic effects. In later years, particularly in the recent Vision series by Tom King and Gabriel Hernandez Walta, we gain further insight into their time together. He flashes back to their troubled marriage, during which time she occasionally referred to him as “a toaster.” While the name was based on a joke that he'd told her, referring to your spouse as an inanimate tool, even lightheartedly, carries with it a certain connotation.
In issue seven, there's a fascinating interaction when Vision goes to confront his son's murderer—and Wanda points out that if he commits murder, he'll just be like everybody else. The Vision responds by expressing that all he ever wanted was to be like everybody else, stunning the necessarily bizarre Scarlet Witch. Therein lies the main failing between the two. Wanda could control, change, and project her own desires onto the Vision without ever really seeing him for who or what he was. While the series mostly focuses on the Vision duplicating Wanda's folly by creating his own intrinsically doomed synthoid family, Wanda's presence is still felt, and the series displays an incredibly sad, although still somehow loyal love between them.
These Vision & the Scarlet Witch series definitely made for some very strange reading. Despite the amount of personal hardship these two experienced together, they never ceased to be two incredibly troubled, tragically mismatched characters. Not every marriage can be a perfect love story, but it's difficult to view them as being anything close to a good match after recognizing the extensive trauma they caused one another over the years.