Thanos
Thanos built his entire philosophy around the concept of inevitability, famously declaring "I am inevitable" with the certainty of one who had seen the future and found it satisfactory. His crusade to eliminate half of all life stemmed from a mathematical conviction that resource scarcity would destroy civilisations regardless of intervention. The Mad Titan devoted centuries to acquiring the Infinity Stones, demonstrating a patience that few mortal beings could comprehend. Yet his inevitability proved contingent upon circumstance, vulnerable to the combined efforts of Earth's Mightiest Heroes.
Time
Time's inevitability operates on an altogether different register. Every process in the known universe submits to its passage without exception or appeal. Stars are born and die according to temporal frameworks spanning billions of years. Entropy increases inexorably, moving all systems toward disorder with the patient certainty of fundamental physics. Unlike Thanos's proclaimed inevitability, which required the Infinity Stones for actualisation, Time's forward march requires no artefacts, no philosophy, no will whatsoever. It simply is, and always has been, the backdrop against which inevitability itself is measured.