What is the opposite of a black hole?
A white hole.
Black holes are astronomical objects that draw in light and matter due to their immense gravitational pull.
Therefore, the opposite of this would be a white hole, which, instead of drawing in matter, would expel matter instead. Theoretically, these objects are impossible, because adding matter to the universe would increase is entropy, and this would violate the first law of thermodynamics, which states that the energy of a system must remain constant.