Same word as unethical:

cheating, corrupt, crooked, dirty, dirty-dealing, dishonorable, disreputable, double-crossing, fake, fishy, flimflam, fly-by-night, illegal, improper, mercenary, scam, shady, sharp, slick, slippery, sneaky, two-faced, two-timing, underhand, unfair, unprincipled, unprofessional, unscrupulous, wrong