Answer 10!
Hamlet makes sure Claudius was the one who killed his father by setting up a play inside the play. This play is exactly what the ghost describes: happy family, happy king, king sleeping under tree, evil king pours poison in his ears and he dies. The queen marries the murderer. After seeing Claudius' reaction to it, Hamlet know for sure that he did it. However Hamlet does not take action right away. When Claudius is praying for forgiveness, Hamlet could've easily killed him then but decides to wait. This shows just how sneaky Hamlet can be.