Some former permanent residents whose status was revoked due to criminal conviction will be permanently inadmissible with no waiver. This is an extremely complex area of immigration law with a lot of court decisions. Most people in this situation are not going to be eligible for a waiver, but it's one where you really need an attorney to carefully study and research the particulars of your case. You probably need to go to an attorney who specializes in criminal aliens, rather than an attorney who specializes in waivers.