Hamlet's father was not an evil spirit. He was trying to protect his wife and especially his son. He wanted to warn Hamlet of the danger he was in, and make sure Hamlet knew what Claudius had done.
I think in terms of the play, he's a Ghost-- a real one. The evidence is that Hamlet is not the only one who can see him. Just like any good ghost story, Hamlet's Father's ghost wants revenge on the man who murdered him and stole his throne and wife.
In a more psychological analysis, the ghost can be seen as the unresolved issues brought up by Claudius' villainy, and the work that must be done to right those wrongs. The ghost represents a call for justice, one that only one person is in any position to do anything about-- Hamlet.
hamlet father is a ghost.in a way that he didn't harm anyone.an evil spirit is one that can harm pple's life.so it is a ghost that is not on rest coz its soul was killed and it want revange.and all people to know what really happened on the death.
It is fact that the revelation of Ghost is supposed to be bad omen.Here we see the father of Hamlet as ghost after death comes to disclose the secret of his death.The disclosure obsessess Hamlet`s mind and he resolutes to take avenge.He takes revenge in which his life is too lost.so the ghost when ever appears it creates problem for mankind.Simultaneously he creates problem and Hamlet loses his life.It means ghosts are nothing else but evil spirits.
I see the ghost, even though other people can see him, as something from Hamlet's imagination. The ghost is really only there to get the plot in motion, and since ghosts don't exist, I think it's all in Hamlet's mind.
In my opinion, he isn't an evil spirit, more like a spirit in distress. He's burning in purgatory for god's sake, that's the whole purpose of the story, to kill Claudius and put his father's soul to rest. It's kinda like what the greeks believe, in the Illiad, Achillies is haunted by patroclus's ghost, Achillies is so heart broken by his death, he doesn't burn his body so Patrolcus spirit is just walking around and he begs Achillies to burn his body so his soul can rest.