Flame Reaver vs Pyron: who would win?

Pyron favored — Slight edge (~55%)

Flame Reaver · Honkai: Star Rail · Base

Tier

3-C, up to 2-A

Attack Potency

Galaxy Level, up to Multiverse Level+

Speed

Ftl+, up to Infinite

Durability

Galaxy Level, up to Multiverse Level+

Pyron · Darkstalkers · True Form

Tier

3-C

Attack Potency

Galaxy Level

Speed

Massively Ftl+

Durability

Galaxy Level

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