The death in 2386 of Icheb, a former Borg drone turned Starfleet officer, whose implants were cut out by black marketeers and who was mercifully killed by Seven of Nine.
The death of Icheb is shown at the start of the Picard episode Stardust City Rag. Icheb, the young Brunali whom Seven of Nine had helped to raise aboard Voyager, was serving as a lieutenant on the science vessel USS Coleman. He was lured into a trap and taken to a facility on the planet Vergessen, where Borg parts were removed from living victims for sale.
The surgeon cut out implant after implant without anaesthetic, looking for a cortical node that Icheb no longer had, since he had given it to Seven years earlier. Seven fought her way in too late. She held him, told him she was sorry and ended his suffering with a phaser shot.
The trap had been set by Bjayzl, a woman Seven trusted while working with the Fenris Rangers. Thirteen years later, in the same episode, Seven goes to Freecloud with Picard's help and kills her.