Dimwits are villains who rarely (if ever) use their heads. In other words, these villains are often seen as dumb and ignorant, and are very likely to foil their own plans or other villains' plans and can even cause them to ruin themselves; this is usually due to poor planning, stupidity, ineptitude, impulsiveness, bumbling, or even slowness. Many of these villains are also Incompetent because of their stupidity. However, there are exceptions in villains who are dangerous because their stupidity causes them to make reckless decisions, an example being Iok Kujan.

However, some of these villainous idiots can be considered NOT particularly dim-witted nor ignorant, as some villains like Wile E. Coyote, King K. Rool and Sylvester can often be considered more careless, silly and sometimes, clumsy or feeble-minded as opposed to outright stupid (much like their heroic counterparts). Furthermore, some of these villains (such as Beavis and Butt-Head and Crash) can be viewed as being Chaotic Neutral, as they may not always be aware of their actions due to their stupidity.

Not to be mistaken with characters who are Mentally Ill (such as Jason Voorhees), or those with genuine learning difficulties (such as the Great Child and Leatherface), as there is a major difference between the two categories. They are also the polar opposite of Masterminds, who are exceptionally intelligent and resourceful characters.

It is needed to note that demons or eldritch abominations that are completely mindless or have zero moral agency can also end up qualifying for this category as those types of villains are known to not use their heads in most cases, and are mindless or cannot comprehend what they do (Azathoth and No-Face who are prime examples of this).

Some shows are made up almost entirely of dimwits, especially a comedy where nobody is succeeding in their goals and possibly being scapegoats. They could have a masterminded game changer as the exception.

Unseen villains usually do not qualify, because they are always not seen, unless there are proofs that the villain is dumb or the villain will be seen at the end.

Villains who have only pretended to be dumb (i.e. William Wharton, Eric Cartman, Doofy Gilmore, Gollum, Stanley Pines and some versions of the Joker) do not count. That is an example of trickery.

NOTE: Dimwits normally do not qualify for Pure Evil as they're intended to be incompetent villains. However, some can qualify if they are somewhat competent (Having enough physical strength, superpowers, wealth and/or authority to compensate for their low intelligence, taking advantage of any opportunities to hurt others or doing actions that are both heinous and stupid, being completely taken seriously by the narrative and fully aware of the damage their actions cause in spite of their stupidity: (e.g. Alan Yates, Joffrey Baratheon, Wyald, President Stone, Bogs Diamond, Colonel Henry Favours, Muscular, Stu Macher, Masayoshi Shido, Rip Blazkowicz, King Runeard, Zorin Blitz, Infinite, Bob Ewell and Evelyn Claythorne).