Who causes hamlets decline and death

I have to write an essay and the topic is: who is the main character that causes the decline and death of hamlet. So far my three main points are 1. Claudius kills king hamlet 2. He has people spy on hamlet and 3. He marries Gertrude. If you guys have stronger points or have any ideas on a creative take I could have on it that would be great. Also if you have any major points that I should include that would be greatly appreciated

Hamlet learns from the Ghost of his father that his father was killed by his uncle, who has since married Hamlet's mother.

Hamlet decides to act crazy while figuring out what to do.

His uncle Claudius sets spies on him because of his crazy behaviour.

Hamlet confirms that the Ghost was telling the truth by putting on a play mirroring the murder of his father. Unfortunately this also tips Claudius off (he was pretty suspicious anyway)

Hamlet catches and kills a spy in his mother's bedroom. Unfortunately it is the king's advisor Polonius.

Claudius sends Hamlet to England.

Polonius's son Laertes comes from France to revenge his father. Claudius tells him that Hamlet had killed Polonius.

Hamlet doesn't get to England because of pirates, and returns to Denmark.

Claudius and Laertes set up a fencing match where Hamlet is to be murdered by an unbuttoned poisoned sword and a poisoned cup of wine. Hamlet gets cut by the poisoned sword but so does Laertes, and Hamlet's mother drinks the poisoned wine. Before he dies, Hamlet stabs and poisons Claudius to death.