"More on the level" refers to being honest, straight-forward, and truthful. Some antonyms for this expression could be "less credible," "shady," "dishonest," "deceitful," "crooked," "dubious," "insincere," "manipulative," "misleading," "unreliable," and "untrustworthy." These words indicate a lack of transparency, and suggest that the person is not trustworthy or sincere. When someone is "more on the level," they are open and sincere in their communications, whereas those who are the opposite of this expression tend to hide their true intentions or manipulate others for their own gain. It is always good to be wary of those who are not more on the level when interacting with them.