Kyora Sazanami vs Gill: who would win?

Kyora Sazanami favored — Slight edge (~55%)

Kyora Sazanami · Kagurabachi · Wielding the Magatsumi

Tier
8-B
Attack Potency
City Block Level
Speed
Massively Hypersonic+
Durability
City Block Level

Gill · Street Fighter · Base

Tier
8-B, up to 6-C
Attack Potency
City Block Level, up to Island Level
Speed
High Hypersonic, up to Speed Of Light
Durability
City Block Level

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