Mega-Megamind vs Kars: who would win?

Kars favored — Slight edge (~55%)

Mega-Megamind · Megamind · Base

Tier

8-A, up to HIGH 6-C

Attack Potency

Multi-City Block Level+, up to Large Island Level

Speed

Hypersonic, up to Massively Hypersonic

Durability

Multi-City Block Level+, up to Large Island Level

Kars · JoJo's Bizarre Adventure · Ultimate Lifeform

Tier

8-A

Attack Potency

Multi-City Block Level+

Speed

Massively Ftl

Durability

Multi-City Block Level+

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