The Red Stone of Aja vs Conrad: 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

Conrad · Berserk · Base

Tier
7-A, up to 6-C
Attack Potency
Mountain Level+, up to Island Level
Speed
Massively Hypersonic+
Durability
Mountain Level+

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