Ducker

Ducker (ダッカー) was one of the 10,000 players who were trapped in «Sword Art Online» and a member of the «Black Cats of the Full Moon» guild. Ducker was a thief build player (which means he was the guild anti-trap and loot chest finding specialist in this case) and was killed along with most of his guild when he triggered a trap that called multiple monsters out and prevented the use of teleport crystals.

Sword Art Online
Before being trapped in the virtual world of Sword Art Online, he was part of his school's tech team. Almost every member of the team entered the virtual world, and there they formed a guild. One day, while they were on the losing side of a monster battle in a dungeon, Kirito rescues them and safely escorts them out of the dungeon. They were thankful for the action and decided to invite the benefactor into their guild, not knowing his true status as a beater, to which Kirito accepts.

A few weeks after Kirito joined the guild, they explored an unexplored area of a dungeon. After Ducker triggered a chest trap, due to his trap disabling skill being too low for that part of the dungeon, the room was sealed in, with an anti-crystal field, preventing the use of crystals, including teleportation crystals, and numerous monsters spawned in the room and attacked the under-leveled players. Ducker was the first member to be killed, soon followed by the rest of his guild members in the room, the only survivor being Kirito, who was a much higher leveled player than the other members.