Arabia Fats vs Mitsuari Ayu: who would win?

Mitsuari Ayu favored — Slight edge (~55%)

Arabia Fats · JoJo's Bizarre Adventure · Base

Tier

10-B, up to HIGH 8-C

Attack Potency

Human Level, up to Large Building Level

Speed

Immobile, up to Speed Of Light

Durability

Human Level

Mitsuari Ayu · Toaru Majutsu no Index · Base

Tier

10-B, up to 9-B

Attack Potency

Human Level, up to Wall Level

Speed

Average Human

Durability

Human Level

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