When a supergiant runs out of fuel, the object formed is either a black hole or a neutron star.
<u>EXPLANATION:</u>
Supergiant are very large stars in the galaxy that end their lives very quickly.
When a supergiant star loses its fuel, it blows itself by a supernove explosion.
When supernove explosion happens, the supernova outshines other stars in the galaxy and then slowly faded away leaving a dense object called black hole or neutron star.
This black hole or neutron star is surrounded by a mass of very hot gas and the elements of the supergiant star get scattered into the space.