Used for something that contains an internal contradiction or mutually incompatible elements; comparative and superlative forms are formed with more/most.
Definitions
self-contradictoryadjective
containing a contradiction within itself; logically inconsistent
The proposal is self-contradictory, because it demands lower taxes and higher spending at the same time.
having statements, ideas, or parts that conflict with one another
Her self-contradictory explanation left everyone unsure of what had actually happened.