Is there a word that describes an inept schemer?

The phrase hoisted on his own petard conveys the concept

to suffer harm from a plan by which you had intended to harm someone else

The phrase is used by Shakespeare in Hamlet

For ’tis the sport to have the engineer

Hoist with his own petard

An engineer is a builder of military equipment, and a petard is a type of bomb to blow a hole in a wall. In effect,

it's amusing to see the would be bomb-builder blow himself up.

The Warner Bros. cartoon character, Wile E.Coyote, is an embodiment of the concept, scheming to destroy his nemesis, The Roadrunner, but constantly being defeated (and injured in grandiose fashion) by his own conniving.