What fundamental property dictates the destiny and evolutionary pathway of any star?

Its mass

The mass of a star upon its formation is the single most important factor governing its entire existence, from its lifespan to its ultimate fate. This initial mass determines the central pressures and temperatures achievable in the core. Stars with higher initial mass compress their fuel more intensely, leading to much higher core temperatures and pressures. This dramatically increases the rate of nuclear fusion, causing them to burn through their hydrogen fuel much faster, resulting in shorter lives, often only millions of years, compared to less massive stars. Conversely, lower mass stars burn slower and can sustain fusion for trillions of years. Mass dictates the pathway, governing whether the star ends as a white dwarf, a neutron star, or a black hole.