A foil when defined is one that by contrast underscores or enhances the distinctive characteristics of another. In the play the two characters which served as Hamlet's foils were Horatio and the Ghost of the late king, who was Hamlet's father. Each served as foils in different aspects of the definition.
I believe that Horatio was Hamlet's strongest foil. He was a fellow student of Hamlet's as well as a good friend. Through the entirety of the play he remained alongside him supporting his decisions and providing him with any information he had. He also shared many of the same traits as Hamlet. He was very brave, as was Hamlet. They both showed this bravery by approaching the ghost when it appeared to them during their watch. Horatio was also loyal to Hamlet in the same way that Hamlet was loyal to his father after he had died, unlike his mother.
The definition of a foil states that this character underscores the distinctive characteristics of another, which is exactly what Horatio did throughout the play. Through his bravery and loyalty he complimented Hamlet and they were able to maintain a stable relationship, for Hamlet was unable to do this with many of the people in his life.
Although many would argue that the Ghost of the late king could most definitely not serve as a foil of Hamlet's, I strongly disagree. The definition of a foil also states that it is one who enhances the distinctive characteristics of another. This is exactly what the ghost did in Hamlet's case. He enhanced his loyalty, by providing him with the proof that he needed so that he could find his Uncle guilty of murder. Hamlet felt he could not let his father down, especially since he had come back to appear...