Adaptational Villainy (or Vilefication) is TV Trope- term found in any media, Related in how a character is given more villainy or antagonist than its source material.
How Exactly Works?
While any related material or source material has character who is originally heroic or good, Sometimes to give him/her a new take, it is tended to be given a more antagonistic take, the Adaptational Villainy is commonly used to villains already, but it is not unheard of used in heroic characters (E.g. King Louie and Sentinel Prime.)
Speaking generally, Adaptational Villainy it serve as way to give a villain more character development and also Hidden Depths.
Heroes in general suffer from cases of Adaptational Villainy (Albeit more downplayed than others), but this of course it's to given a more updated characterization or in the inverse of the case "Flanderization", (E.G. Catwoman, Superman, and Batman)
While it's rare that a Complete Monster suffer from Adaptational Villainy, there are cases that those villains are more amplified in terms of vileness (For Example: Lord Embryo, Superboy-Prime and Some incarnations of The Joker), in other hand it is far more rarely than an actual master of horrors suffer from this case, Albeit it can happen if the character need a expansion of his/her character (E.g. Desghidorah, Tengu Shredder, Utrom Shredder and Shinnok).
This for writing is more often criticized by some due to being altering the original source material (Books, Films, Etc), However it can give the villain a more complex explanation of his/her villainy.