Magnus Chase vs Kai the Collector: who would win?

Kai the Collector favored — Slight edge (~55%)

Magnus Chase · Percy Jackson · Base

Tier
7-C
Attack Potency
Town Level
Speed
Superhuman, up to Subsonic
Durability
City Block Level

Kai the Collector · Kung Fu Panda · Base

Tier
7-C
Attack Potency
Town Level
Speed
Supersonic+
Durability
Town Level

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