Demons are villains who are malevolent beings, normally possessing many supernatural abilities like influences over different realms and dimensions, putting them above your average monsters. Due to their ability to possess, corrupt and brainwash, demons are the most feared and dangerous beings. Some demons cannot qualify, seeing that they cannot distinguish right from wrong since they only know how to do evil things. However, Pure Evil demons can qualify if they have a distinct moral agency and meet all other criteria for Pure Evil. They are the malevolent counterparts of Pure Good Demons and opposites of Angels.

Examples include; Aku, Gyokko, Demon King Jackal, Serrator, Enmu, Apep, Angra Mainyu, Grandmaster Nimzo, Yuuki Terumi, Judge Holden, Mortamor, Cardinal Sin, Ke-Pa, Void, Orgodemir, Bloodwolf, Sauron, Azazel, Dark Lugiel, Ganondorf, Ghirahim, Demise, Novisor, Mephiles the Dark, Morgoth, Malefor, Jindiao, Lucifero and the Scarlet King.