Aventurine vs Coily Rattler: who would win?

Aventurine favored — Favored (~65%)

Aventurine · Honkai: Star Rail · Aventurine of Stratagems

Tier

3-C, up to 2-A

Attack Potency

Galaxy Level, up to Multiverse Level+

Speed

Ftl, up to Infinite

Durability

Galaxy Level

Coily Rattler · Kirby · Base

Tier

4-A

Attack Potency

Multi-Solar System Level

Speed

Massively Ftl+

Durability

Multi-Solar System Level, up to Low Multiverse Level

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