For me, the most frustrating situation, is when your pilot has heroically disabled a Pirate Kestral, or Corvette etc. in a small ship such as a scoutship, or Courier, and an irritating little Manta, or Confed Patrol ship comes out of the blue, and blows it up before you can board it. Maybe the second most frustrating thing is when you have disabled a juicy prize, but you're too near the "wall" of the system, and the disabled ship drifts accross the wall, and is sitting there out or reach.
Any other candidates ??
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Lightspeed: 11.78 inches/nnanosecond