Jiji vs Gary Mitchell: who would win?

Jiji favored — Slight edge (~55%)

Jiji · Dandadan · Accessing Ki

Tier
9-A, up to HIGH 8-C
Attack Potency
Small Building Level+, up to Building Level+
Speed
Superhuman
Durability
Building Level

Gary Mitchell · Star Trek · Base

Tier
8-C, up to HIGH 6-A
Attack Potency
Athlete Level, up to Multi-Continent Level
Speed
Athletic Human, up to Massively Hypersonic+
Durability
Building Level, up to Multi-Continent Level

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