For context, the Little One once activated a device that transformed all of Teyvat (an Earthlike planet) into raw, programmable energy, along with fusing all conscious life into one being—a God for whom Time itself loses meaning. This specific phrasing is significant since Time is one of Teyvat's Primordial Powers, alongside Life, Death, Space, and Reason. Exemption from Death in particular presents as flawless ressurective immortality so potent that attempting to kill such a being is considered a logical paradox. As such, I assume attacks like "punch really hard" won't work. Plus, you'd basically be attacking a ghost. 

The initial explosion was Star Level based on running e=mc^(2) on Earth's mass, though the fate of the Traveler is left ambiguous so we can't confidently say whether it would absorb the consciousness of non-native Teyvatians. For the sake of not trying to figure out who has a "will to rival the world," I'm ignoring the assimilation process and assuming that the Little One nukes whatever planet the character happens to be on at a given time. 

The "Little One get your ass home" tier is reserved for those select few characters whose mere presence on the planet would prevent the nuke without the need for time travel or retcons and who aren't Giorno.

Death Battle combatants ranked by how they do against the Traveler's pet lizard