Mob Psycho 100
Both come from ONE and share the same core trick: absurdly overpowered protagonists used for comedy, then surrounded by surprisingly sincere character arcs. Mob Psycho 100 is more emotionally introspective, but the humor-action blend feels extremely familiar.
My Hero Academia
Both play in superhero worlds with rankings, public image, flashy powers, and different ideas of what makes someone a hero. My Hero Academia is more earnest and school-based, while One Punch Man is more satirical, but fans of hero society usually enjoy comparing the two.
The Disastrous Life of Saiki K.
Saiki K. shares the joke of an absurdly overpowered protagonist who is bored, annoyed, or uninterested in using his powers dramatically. It has almost no action stakes compared to One Punch Man, but the deadpan comedy of unlimited power is very close.
Tiger & Bunny
Tiger & Bunny also focuses on professional superheroes, rankings, sponsorships, and the public performance of heroism. It is more character-drama than parody, but it scratches the same interest in a structured hero industry.
Gintama
Gintama gets recommended because it has the same willingness to parody genre tropes while still delivering real action when it matters. It is much longer and more reference-heavy, but fans who like One Punch Man's comedy-action switch often enjoy it.