The Red Stone of Aja vs Beast (Undead Unluck): who would win?

The Red Stone of Aja favored — Slight edge (~55%)

The Red Stone of Aja · JoJo's Bizarre Adventure · Maximum Power

Tier
7-A
Attack Potency
Mountain Level+
Speed
Speed Of Light
Durability
Unknown

Beast (Undead Unluck) · Undead Unluck · Base

Tier
HIGH 7-A
Attack Potency
Large Mountain Level
Speed
Massively Hypersonic+, up to Ftl+
Durability
Large Mountain Level

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