Anankos vs Iansan: who would win?

Anankos favored — Slight edge (~55%)

Anankos · Fire Emblem · Anankos

Tier

7-B, up to 4-A

Attack Potency

City Level, up to Multi-Solar System Level

Speed

Massively Hypersonic

Durability

City Level, up to Multi-Solar System Level

Iansan · Genshin Impact · Base

Tier

7-B, up to 6-B

Attack Potency

City Level, up to Country Level

Speed

Supersonic+, up to Relativistic

Durability

City Level, up to Country Level

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