Mondo Owada vs Lord Boros: who would win?

Lord Boros favored — Slight edge (~55%)

Mondo Owada · Danganronpa · Base

Tier
HIGH 7-C
Attack Potency
Large Town Level
Speed
High Hypersonic
Durability
Large Town Level

Lord Boros · One-Punch Man · Base

Tier
HIGH 7-C, up to HIGH 6-A
Attack Potency
Large Town Level, up to Multi-Continent Level
Speed
Massively Hypersonic+, up to Relativistic+
Durability
Large Town Level, up to Continent Level

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