This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Fairy Dance Of Death
The first thing Salamanders do when death-game announcement is made: Attacks Imps en masse while everyone is still figuring what to do. Keep in mind what Nerve Gear does when player dies in-game...
In chapter 38 it's quite explicitly implied that one of the Salamander tried to rape Yuuki, during the attack that killed her sister...
Xaxa takes time out to hunt down and kill kids in the Sewers without any hesitation.
By the time half a year has passed in the game a full 1/4 of the Undines are dead, the healers of the game, most done by P Ks rather than monsters in the first month. The less of them there are then the more players that can't be healed or rezzed.
The fact that there are NPCs who promotes player-killing.