Iron. However, heavier elements are created in supernova explosions and scattered back into the interstellar medium, to be parts of new stars and planetary systems.
It is cool how elements are made.
My chemistry prof told the class that it is thought that there are more natural elements than is currently known, we just don’t have yet the technological means of detecting those elements.
Scientists even think they’ve figured out the shape of the electron pathways of the next shell.