The blast also confirmed that so-called pair-instability supernova exist, this type of supernova has long been a topic of debate as there were severe doubts that stars that massive could ever form.
In a pair-instability supernova, the star has neared the end of its life and exhausted its main supplies of hydrogen and helium, leaving it a core of mostly oxygen. In smaller stars, the core continues to burn until eventually it is all iron, then collapses in a Type II supernova, leaving behind a remnant black hole or neutron star.More details at Space.com.
But in the case of an extremely massive star, while its core is still made of oxygen, it releases photons that are so energetic, they create pairs of electrons and their anti-matter opposites, positrons. When the matter and antimatter meet, they annihilate each other. This reaction reduces the star's pressure, and it collapses, igniting the oxygen core in a runaway nuclear explosion that eats up the whole star, leaving no remnant at all.