The Antagonist should in some way reflect the Protagonist, that is, your MC. While, yes, in some instances the protagonist is their own antagonist, this is for the external antagonists out there. However, that’s not to say that the antagonistic qualities of your MC can’t be personified and developed in this spread as well.
This is an opportunity do really bring depth to your protagonist and your antagonist. If they are completely at odds with one another, then their goals should be at odds. If they’re similar, then it gives the opportunity for conflict within their opposition of each other. Meta conflict, if you will.