|“||I shall not be defeated! If you defeat me, I will simply return, again and again! I am immortal! I cannot be vanquished!||„|
|~ Erazor Djinn|
Villains that are impossible to kill, which is referred as "complete immortality". While in other cases it simply means they have an infinite unnatural life span but can die if killed through trauma, which is referred to as "biological immortality". Sometimes, they achieve their immortality through special magical items that, if destroyed, will kill them or leave them vulnerable to death, such as Davy Jones' Heart, Lord Voldemort's Horcruxes, or Kel'Thuzad's Phylactery.Characters like Sigma can simply comeback an infinite number of times regarding if his cognitive curcuits aren't completely destroyed.
This can sometimes be an element to a Tragic Villains, as they cannot hold on to love ones (sometimes causing them to become bitter and angry).