* Im- (Imperfect): Not perfect, flawed.
* In- (Inperfect): While this is technically a prefix, it's not used in English as it is redundant with "imperfect."
* Re- (Reperfect): To make perfect again.
* Un- (Unperfect): This is not a common word, but it could technically mean "not perfect."
* Over- (Overperfect): To be excessively perfect, perhaps to the point of being unnatural.
* Pre- (Preperfect): Perfect in advance, perhaps referring to a state that existed before perfection was achieved.
* Super- (Superperfect): Beyond perfect, exceeding perfection.
The best prefix to use will depend on the context and the specific meaning you want to convey.