Ghast vs Pegasus: who would win?

Pegasus favored — Slight edge (~55%)

Ghast · Minecraft · Base

Tier

9-B, up to 8-C

Attack Potency

Wall Level, up to Building Level

Speed

Average Human, up to Subsonic

Durability

Small Building Level

Pegasus · Dungeons & Dragons · Base

Tier

9-B, up to 9-A

Attack Potency

Wall Level, up to Small Building Level

Speed

Relativistic+, up to Ftl

Durability

Wall Level, up to Small Building Level

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