Actually, only a supernova or equivalent energy magnitude event.
Fusion only releases energy up to iron. Creating heavier elements consume energy in the reaction rather than releasing it, therefore cannot sustain a reaction.
Fission goes the opposite way. Heavier elements than iron release energy.
I think the inside of a star is not perfectly clear-cut. Various elements get created and cycle, with only the energetically-favorable ones accumulating. It's not altogether unlike chemistry.
What little I know of this comes from wikipedia, but I think there are other ways to synthesize elements apart from fission and fusion. Sometimes they simply catch a neutron, and the decay of a particle produces a different element.
Fusion only releases energy up to iron. Creating heavier elements consume energy in the reaction rather than releasing it, therefore cannot sustain a reaction.