Kamen Rider X vs Kiran (Fire Emblem): who would win?

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

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

Tier

1-C

Attack Potency

Complex Multiverse Level

Speed

High Hypersonic, up to Ftl+

Durability

Multi-City Block Level, up to Complex Multiverse Level

Kiran (Fire Emblem) · Fire Emblem · Book I

Tier

1-C

Attack Potency

Complex Multiverse Level

Speed

Superhuman, up to Massively Hypersonic+

Durability

Unknown

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