Hamlet could kill Claudius at this moment but does not because he wants to kill the king in the midst of sin, not prayer. This moment provides dramatic irony because readers know what Hamlet does not: the king is not praying.
King Claudius is a fictional character and the main antagonist of William Shakespeare's tragedy Hamlet. King Claudius is the villan of the play.
In tha play, Hamlet wants to kill Claudius three times.