Mega Man (Megamix/Gigamix) vs Kronos (Riordan): who would win?

Kronos (Riordan) favored — Slight edge (~55%)

Mega Man (Megamix/Gigamix) · Mega Man · Base

Tier

5-C, up to 5-B

Attack Potency

Moon Level+, up to Planet Level

Speed

Subsonic, up to Massively Ftl

Durability

Moon Level+, up to Planet Level

Kronos (Riordan) · Percy Jackson · True Form

Tier

5-C, up to HIGH 4-C

Attack Potency

Moon Level+, up to Large Star Level

Speed

Massively Hypersonic, up to Massively Ftl+

Durability

Moon Level+, up to Large Star Level

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