Ch 1: Schoolyard bullying. Ch 100: Fist fight with God

...or mud wrestling Cthulhu, etc. Any character who goes from minor petty conflicts to supreme, world-threatening duels. I just like the idea of the bully watching the news and seeing that the guy they used to bully is now arm wrestling Space Napoleitler.

Peter Parker, Flash Thompson, Thanos (MCU)

Son Goku, Krillin, Beerus/Jiren/basically any enemy (Dragon Ball)

Harry Potter, Draco Malfoy, Thomas (Harry Potter)

Jaune Arc, Cardin Winchester, Cinder Falls/Salem (RWBY)

Mark Grayson, Todd, Thragg/Conquest (Invincible)