I think one of the more oblivious and not so negative FOIL is Horatio, through all the madness they remain friends. In the play you get to experience the trust and loyalty between Hamlet and Horatio. The two characters are very much alike. They both show acts of kindness or softer side. I think Shakespeare use Horatio to show a more positive happy side of Hamlet.
Though Shakespeare had positive foils to bring out the best in hamlet he also used negative FOILS like Claudius. I think between Hamlet and Claudius you can see the ultimate betrayal. In the play you expect Hamlet to be me or rude to Hamlet however we see how intelligent hamlet is, he never reveals to Claudius what he know or things, he simply keeps a close eye on him.
Unfortunately most of the other foils are more negative like Fortinbras. Fortinbras and hamlet both want to avenge their father’s death. However the characters share a personality. Instead of attacking at anytime or letting anyone lead on to them, they patiently wait for the right time. The willingness and need to do the right thing is apparent in both characters.
Finally I think another important FOIL is Laertes large desire to avenge his father’s death, putting him in the same boat as Hamlet. Because Hamlet kills Laertes’s father he is now like Claudius killing his father. The different situations cause the FOILS to in a sense cross a paths, and better portray Hamlet. In conclusion I think Shakespeare uses FOILS to show the negative and positive characteristics of Hamlet.