Oh god, infinite patrol mission.
I accepted a patrol mission at Grand Exchange I believe. It would be your normal pirate stomp, nothing amazing. Here's the hitch: Grand Exchange is connected to a 4-sector Xenon-controlled part of space. This means there's pretty much constant trains of a Xenon Q/PX/P leading a bunch of Xenon M/L/Ns to the system and kicking around the local stations and police forces. Patrol missions only complete/advance when you kill all enemies of the government in the sector I think, not just the pirate hordes that spawn. The Xenon come in faster than I can kill them, my military backup and the pirates have long since died, it's just me and the occasional freighter escort team.
Aside from probably being the worst place in the universe to start a trading empire, Grand Exchange is also the place where patrol missions go to die, except they stay in your mission log... The original reward was 250,000 credits + kill credits, I racked up 500,000 credits in kills before I got bored and left. It's a good place to cap some Xenon ships (since you can apparently make the AI fail and capture them) if you can deal with everything else with the group. But, holy hell, there's just so many Xenon ships that unless you're rolling with your own personal army you could never kill them fast enough without dying.