The term "not crooked" denotes straightness, honesty, integrity, and reliability. Synonyms for this term could be "upright," which signifies a person's moral and ethical qualifications. "Honorable" could also be a synonym, which implies a sense of trustworthiness and respectability. "Direct" suggests straightforwardness in communication or behavior. "Moral" is another option, which implies abidance to moral standards and principles. "Unbiased" is another synonym which refers to impartiality and treating all parties equally. Whatever term you may use, it all sums up to the same idea, which is something that is not bent or distorted and exhibits trustworthiness and honesty.