"Emotions are the hidden reasons for action." Explore the emotions behind action in Hamlet AND in a related text.

Hamlet's actions are fueled by a desire for revenge, prompted by his grief over his father's death and his mother's remarriage. These events shake Hamlet's sense of the justice in the world and make him want to "set it right" though actions that will restore his emotional equilibrium.
Ophelia's rejection of Hamlet's affections seems to hurt him deeply, prompting his "Get thee to a nunnery" attack on her. Added to his other sorrows, this alienation from Ophelia's affections seems to prompt his despair and the "To be, or not to be" soliloquy.
In the final scene, Hamlet's ability to finally take revenge on Claudius is prompted by his indignation over the fact that Claudius's and Laertes's trickery has led to Gertrude's death. In this last moment, Hamlet acts with justifiable emotion in finally murdering Claudius, an action he seemed unable to perform in his more rational moments.
If you want to stay with the Shakespearean canon for responding to this question, either Othello or King Lear offer rich material. Othello's jealousy, or his fear than Desdemona may no longer love him, precipitates a series of horrific actions, ending in her murder and his suicide. Lear's desperate need to know his daughters love him as he prepares for his final years leads him to divide his kingdom and banish his one faithful daughter, Cordelia. The other two daughters conspire against each other over their attraction to Edmund, leading also to a murder-suicide ending.
While these emotions may not be entirely hidden, the actions that ensue from them seem disproportionate, suggesting an intensity of feeling not otherwise understood.