The conclusion of your essay forms part of the framing of your argument through the essay's structure. This means that you should not be saving up material for the end, hoping to surprise your reader by a sudden "twist", since such a structure is only appropriate to creative writing. If you find in the course of writing your essay that an important new idea emerges somewhere near the end, you should consider overhauling the structure so that the new idea comes earlier on, since this will improve the effectiveness of the essay.
But you have also not provided adequate framing for your argument if your conclusion simply repeats or summarizes points made earlier in the essay, since this adds nothing to your reader's understanding of what you are trying to say. Instead, in the conclusion you should aim to place your arguments in the wider context of the academic field, or key issues to which they relate, perhaps by referring back to the context you have already established in the introduction.