used to emphasize sth that is expressed clearly and directly, especially a criticism 直截了当地说，不客气地说（尤指批评）
Not to put too fine a point on it, I think you are lying.
不客气地说，我认为你在撒谎。
used in an ironic way to introduce a very strong and usually critical statement不客气地说（用于讽刺，引出语气较重、通常为批评的话语）
Not to put too fine a point on it, (but) his suggestions have been worthless.
不客气地说，他的建议毫无价值。