The 6 Stages of Villain Grief
Villains die. this is a natural part of writing fiction. However, sometimes a large or long-running media franchise kills off one of their big name, popular villains and then regrets it. These are the stages such a franchise might go through in the aftermath, a kind of writer's grief, mourning the loss of a great storytelling element.
There is no real progression here. These stages may appear in any order or even simultaneously.
Stage 1: A Clone in All But Name
A new villain appears with a suspiciously familiar personality, powers, and goals to the dead villain, but with a different name and backstory. As they do not have the same history as the dead villain they often don't get any traction and are killed off quickly.
Stage 2: The Vengeful Sibling*
A brother or sister to the dead villain who was never mentioned previous to their death appears to take vengeance on whoever killed them, and/or they didn't actually care all that much and are just here to take over as the next big threat.
*Sometimes a different family member or an exceptionally faithful lackey instead
Stage 3: The Long-Lost Offspring
A son or daughter of the villain who was estranged from/hidden by/ kept secret from the dead villain shows up and becomes a major plot point. Often not evil, and likely to take a more anti-hero role, but if a villain may follow the same path as stage 2. Often used for either angst potential about their unwanted connection to their infamous parent or as an exploration of the nurture vs nature debate.
Stage 4: A Clone but Literally This Time
Someone has cloned the dead villain. The clone may or may not have the same personality or goals as the original, but they will have their appearance and powers. May be used as a lead up to stage 6.
A new villain or villainous organization appears, and in order to take advantage of the dead villain's history and influence in the series a series of retcons are made to establish the new villains were really behind everything all along and the dead villain was just one of their pawns.
Stage 6: Fuck It Bring Them Back!
Somehow, the villain has returned.