Kamen Rider Stronger vs Alfonse: who would win?

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

Kamen Rider Stronger · Kamen Rider · Skyrider, Super-1 & ZX

Tier

1-C

Attack Potency

Complex Multiverse Level

Speed

High Hypersonic, up to Massively Ftl+

Durability

Complex Multiverse Level

Alfonse · Fire Emblem · Book I

Tier

1-C

Attack Potency

Complex Multiverse Level

Speed

Superhuman, up to Massively Hypersonic+

Durability

Complex Multiverse Level

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