Unlike black holes, neutron stars can not grow infinitely: by typing in a certain size, they easily collapses into the same black hole. The maximum possible mass for them is estimated at just 2.16 times the mass of the Sun.
After a large star dies in a supernova explosion and resets the substance of its outer shells, the remnants can collapse. In the extreme case, a black hole is formed, but if the mass of the star's core is not enough, an incredibly dense neutron star appears in its place.
It is worth recalling once again that neutron stars are one of the densest objects in the universe. Having a size of just over 10 km in diameter, such a star will weigh twice as much as the Sun and create the corresponding extreme gravitational field.