Brainiac (Lego) vs Billy Kid: who would win?

Billy Kid favored — Slight edge (~55%)

Brainiac (Lego) · DC · Base

Tier
8-C, up to 5-B
Attack Potency
Building Level, up to Planet Level
Speed
Peak Human, up to Superhuman
Durability
Wall Level

Billy Kid · Zenless Zone Zero · Base

Tier
8-C
Attack Potency
Building Level
Speed
Superhuman, up to Massively Hypersonic
Durability
Building Level

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