Known as the "All-fair," Eadwig died before he was twenty, regretted by few. During his short reign he managed to antagonize most of the clergy, particularly the influential Bishop, Dunstan. The roots of their feud were sown on Eadwig's coronation day, when at some point in the proceedings Dunstan and some others noticed that Eadwig was absent. They went in search of him and found Eadwig closeted with one Aelfgifu and her mother. Dunstan did not approve of the way Eadwig was conducting himself with the girl, whether because of the actual behaviour or because of Dunstan's Tertullian-like views on women ("women are instruments of the devil"), we don't know. Suffice it to say that Dunstan broke up the little party and dragged Eadwig back to hobnobbing with officials, earning not only Eadwig's dislike but also that of Aelfgifu's mother, who, when Eadwig married Aelfgifu shortly after, used her position as mother-in-law to put in a bad word for Dunstan whenever occasion offered. historians generally consider her hand to be behind Eadwig's depriving Dunstan of his possessions and exiling him. (Dunstan later came back, strong as ever, and was involved in British politics for a few more decades until his death in 988.)
Two years after being elected by the witan, the councils of Mercia and Northumbria voted to dethrone Eadwig, with the result that for the next two years Eadwig's brother Edgar became king in those areas.
Concerning Eadwig's death, little is said. One of the chroniclers related a lurid little story that may or may not be true; it is true, however, that the chroniclers were generally hostile to Eadwig, so they would not have been as likely to invent this story, which puts Eadwig in a sympathetic light. However, they do seem rather to relish it, so perhaps the whole thing is simply wishful thinking. But for what it's worth:
Aelfgifu, the "strumpet," as one chronicler calls her, had her face branded (possibly in front of Eadwig) and was exiled to Ireland. When her wounds healed she unwisely returned, only to have the tendons of her legs ripped out, of which wounds she died some days later. Eadwig dies soon afterwards, apparently of shock or heartbreak; in any case, we do know certainly that he died suddenly, leaving the entire kingdom free for Edgar's rule.