Alastor vs Sisters: who would win?

Alastor favored — Favored (~65%)

Alastor · Hazbin Hotel · Base

Tier
LOW 7-C
Attack Potency
Small Town Level
Speed
Subsonic, up to Supersonic+
Durability
Building Level, up to City Block Level+

Sisters · Toaru Majutsu no Index · Last Order

Tier
LOW 7-C
Attack Potency
Small Town Level
Speed
Average Human
Durability
Human Level

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