Itsuwa vs Soldier Boy: who would win?

Itsuwa favored — Slight edge (~55%)

Itsuwa · Toaru Majutsu no Index · Base

Tier

9-C, up to 8-B

Attack Potency

Street Level, up to City Block Level

Speed

Peak Human, up to Supersonic

Durability

City Block Level

Soldier Boy · The Boys · Base

Tier

9-C, up to HIGH 8-C

Attack Potency

Street Level, up to Large Building Level

Speed

Athletic Human, up to Subsonic+

Durability

Large Building Level

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