Hamlet gives his first soliloquy in Act 1, Scene 2, and it's here that we learn of his depression, his suicidal tendencies, and (most importantly) his scorn for his mother's decision to remarry. Indeed, Hamlet's complaint within this soliloquy is not only that his mother remarried, but that she chose to remarry so soon after his father's death. Take, for instance, the following lines: "That it should come to this! / But two months dead! Nay, not so much, not two" (139-140). Following these lines, Hamlet shifts his attention from his contemplation of suicide and his general displeasure with the state of the world to a more focused complaint against his mother's swift second marriage. The rest of the soliloquy picks apart this fact, as Hamlet condemns his mother for her decision. For instance, Hamlet says, "O God! a beast that wants discourse of reason / Would have mourn'd longer" (153-4), and his decision to compare his mother to a beast shows us just how angry he is. As such, in this soliloquy it's safe to say that Hamlet mainly complains about his mother's decision to remarry and the speed with which she made this decision.