Daikaiju of the Meireki Era vs Captain Cosmic: who would win?

Captain Cosmic favored — Slight edge (~55%)

Daikaiju of the Meireki Era · Kaiju No. 8 · Modern

Tier
HIGH 6-B, up to HIGH 6-A
Attack Potency
Large Country Level, up to Multi-Continent Level
Speed
Speed Of Light, up to Ftl
Durability
Continent Level, up to Multi-Continent Level

Captain Cosmic · Invincible · Base

Tier
HIGH 6-B, up to LOW 5-B
Attack Potency
Large Country Level, up to Small Planet Level
Speed
Massively Ftl+
Durability
Large Country Level, up to Small Planet Level

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