Armin Arlert vs Kamen Rider Gai: who would win?

Kamen Rider Gai favored — Slight edge (~55%)

Armin Arlert · Attack on Titan · Titan Form

Tier

HIGH 7-C

Attack Potency

Large Town Level

Speed

Subsonic, up to Supersonic

Durability

City Block Level+

Kamen Rider Gai · Kamen Rider · Kamen Rider Gai

Tier

HIGH 7-C

Attack Potency

Large Town Level

Speed

Superhuman, up to Supersonic

Durability

Large Town Level

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