An incongruent person is a liar but a liar might not be incongruent just that he lies generally about things in order not to be punished or termed bad.
But an incongruent partner or person will have a way of telling you sweet things knowing he might nit be able to do them so that he keeps your mind and heart at his control. Just put manipuative as @greenrun rightly put for us.
Anyone can lie but not all are incongruent. Hope I have been able to answer your question. I also want more people to give their opinions too.
Thanks so much