Gone Forever

When you can't respawn.

They're dead. They're dead, and there's nothing you can do about it. There is no amount of Revival Spells, Potions, or Crying you can shove into their body that can fix it. They're just dead.

Instances of Forever Ded
Real life: Death. When somebody dies in real life, they cannot hit Respawn, nor can they start a new world, nor can they hack the "game" to make it look like they didn't die. They're just... ded. Forever Ded.

Minecraft: Hardcore. Upon creating a world, you can change from Survival or Creative to Hardcore, a challenging gamemode for people who want to die. When you start playing in that world, you cannot change your difficulty (it's Forever Locked on Hard, hence the name Hardcore) or heal easily. Even your health meter is giving you a Glare Of Hellfire And Spiteundefined. Once you die, you're Forever Ded and have no choice other than enter Spectator Mode (a version of gameplay where the only thing you can do is fly around and look at everything) or delete that world forevar.