There is currently no known physical process on how to destroy a Black Hole, but there is the theory that hawking radiation could destroy a black hole after a long period of time.
This theory was proposed by physicist Stephen Hawking, the theory suggests that black holes emit radiation due to quantum effects near the event horizon.
After an incredibly long time this radiation could cause the Black Hole to lose mass and eventually “dissapear” completely.
This process would take ages (far longer than the universe’s current age).
This has been an MIS Blog Post.