Mila vs Atalanta: who would win?

Atalanta favored — Slight edge (~55%)

Mila · Fire Emblem · Base

Tier

HIGH 6-C, up to 4-A

Attack Potency

Large Island Level, up to Multi-Solar System Level

Speed

Superhuman, up to Massively Hypersonic

Durability

Large Island Level, up to Multi-Solar System Level

Atalanta · Nasuverse · Base

Tier

HIGH 6-C, up to LOW 6-B

Attack Potency

Large Island Level, up to Small Country Level

Speed

Relativistic+, up to Ftl

Durability

Island Level

A heuristic estimate from normalized VS Battles Wiki stats: tier, attack potency, speed and durability.