Villains who are more likely to accidentally foil their own plots than the heroes they're fighting against (unless if said heroes are the same) due to stupidity, cowardly behavior, weakness, equally more incompetent henchmen, or arrogance on their part. Thus, they can be easily defeated, and often hit the Scapegoat category because of this.

Incompetent villains mostly appear in comedies - where it is expected from the audience to see the main evil-doers or their henchmen fail miserably (such as Bebop & Rocksteady) - and most cartoons (e.g. many Looney Tunes villains), but can appear as well in serious or even mature stories - if this is the case, they are often Comic Reliefs. An example is Phil Cassidy. Evil organizations and corporations can also be labeled as incompetent, if most of their agents are themselves incompetent. The Team Rocket is a good example of this.

Incompetent villains can also be characters who have schemes that are ultimately stupid, pointless or do little to cause chaos. Sometimes their attempts at evil blow up in their faces by either causing them great harm or even aiding the heroes; thus, these villains are not really much of a threat but they can occasionally be dangerous or even intimidating. Additionally, characters who are stated or made out to be smart in the media they appear in, or even masterminds, such as  Dr. Neo Cortex, and Krang can still be classified as incompetent if they meet any of the previous qualifications.

For obvious reasons, such villains are likely not successful, but in certain cases, they CAN still succeed in their goals, notably if they have the help of much more frightening and competent villains, or just with luck.

Pure Evil villains will NEVER fall under Incompetent as they are capable of committing horrific acts and causing serious problems in a story which actually makes them competent and very formidable.

Even if, in very rare cases, some Pure Evil are somewhat incompetent (e.g. Shou Tucker, Chaka and Joffrey Baratheon) they should go under the Dimwits, Cowards or Weaklings categories instead.