My god man, now what am I going to do with you?! You've done nothing but screw up! You've walked off bases, you've been smashed by boulders, you've been run over by diesel trucks. And don't blame the equipment. The equipment is good. It's ACME equipment! You're a coyote, be wily! All right, now buck up and let's see a little smile.
~ Mr. Chairman ranting to Wile E. Coyote about his incompetence.

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 stupiditycowardly behaviorweakness, equally more incompetent henchmen, or arrogance on their part. 

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 CassidyOrganizations 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. Ivo Eggman Robotnik, 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. They can also be successful if they do not have any real goal aside causing chaos or helping the main villain who succeeded.

Even if they do not display remorses, there is still a slight chance that they reform themselves and definitely abandon their evil schemes, especially if they realize that such schemes will never succeed or if they will never beat the heroes, due to their repetitive failures or lack of strength.

Keep in mind that some Incompetent villain can still perform wicked or even horrendous acts - such as Kay, who committed several rapes and murders before his arrestation - but their inability to fight back must remain prominant in order to qualify.

However, 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.