Rainbow Dash (Human World) vs Phoenix Ikki: who would win?

Rainbow Dash (Human World) favored — Slight edge (~55%)

Rainbow Dash (Human World) · My Little Pony · Pony-Up Form

Tier

2-A, up to LOW 1-C

Attack Potency

Multiverse Level+, up to Low Complex Multiverse Level

Speed

Ftl, up to Infinite

Durability

Multiverse Level+, up to Low Complex Multiverse Level

Phoenix Ikki · Saint Seiya · Phoenix God Cloth

Tier

2-A, up to LOW 1-C

Attack Potency

Multiverse Level+, up to Low Complex Multiverse Level

Speed

Supersonic, up to Infinite Speed

Durability

Multiverse Level+, up to Low Complex Multiverse Level

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