One Day All This Will Be Yours by Adrian Tchaikovsky

In a future where time travel is possible, a war has ravaged the timeline, leaving behind a lone survivor who has taken it upon himself to ensure that no one else can meddle with the past or future. Living in isolation at the end of time, he meticulously destroys any time machines that appear, determined to prevent another catastrophic temporal conflict. However, his solitary existence is disrupted when a group of travelers arrives, challenging his beliefs and forcing him to confront the possibility of a different future. This darkly humorous tale explores themes of power, responsibility, and the consequences of playing god with time.