There were several villains at the head of several factions in Zeta Gundam, but one of the most impressive was the dashing Paptimus Scirocco. While the Jupiter Fleet was a relatively small faction during the Gryps War and the conflict for supremacy over the Earthsphere and Space, they had a number of huge advantages which made them a deciding factor in the outcome of the various arcs that came together at the end of Zeta.
The Jupiter Fleet had been absent, on their mission to mine Jupiter gas, during the One Year War. They arrived back in Earth orbit at a time in which their strength would be sufficient to act as “kingmaker” among the battered warring factions. Scirocco uses this to pull a major coup and and become the defacto head of the Titans. Most importantly, Scirocco was a brilliant mech designer who developed ultra-high-powered custom Mobile Suits optimized for use in Jupiter’s gravity well. Needless to say, these mech are big and fast and monstrous. The PMX-000 Messala, the PMX-001 Pallas Athena, and the PMX-002 Bolinoak Sammahn were all forces to be reckoned with, but were eventually handed down to the various female pilots Scirocco had seduced to his cause. Why? Because he had The O.
The O was big and bulky looking, but the thing was fast, tough, and fought like a damn Asura with its quad beam sabres.
The O had a fusion reactor with 1840 kW output, 1.57G max thrust, 4 0.39 MW beam sabers, and a 2.6 MW rapid recharge beam rifle. It was equipped with an advanced psychommu bio-feedback control system.
Spoiler: even though the hero is able to beat this thing, it manages to fry his brain and turn him into an invalid in the process.