Bakunawa vs Kei Uzuki: who would win?

Bakunawa favored — Slight edge (~55%)

Bakunawa · Dungeons & Dragons · Base

Tier
HIGH 8-C, up to 8-A
Attack Potency
Large Building Level, up to Multi-City Block Level
Speed
Relavistic, up to Ftl
Durability
Large Building Level, up to Multi-City Block Level

Kei Uzuki · Sakamoto Days · Current

Tier
HIGH 8-C
Attack Potency
Large Building Level
Speed
Hypersonic+
Durability
Large Building Level

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