Dishonesty
Again we can go to The 42 Laws of Ma'at for this:
"I have not lied."
This clearly shows that Amun does not approve of lying, and that lying is worthy of not being able to make it into the Duat. Lying can be likened to Apep. Apep, God's enemy, is also known as the Uncreated One and his actions are known to go against Ma'at and "Uncreate" as it were, the creations of Amun. This of course is not good or approved by Amun. Lying, in a way, is like Uncreating to truth that you know is in your heart and mind. And Amun is a God of truth. Therefore, intentionally telling an untruth is as despised by Amun as Apep.
"I have not lied."
This clearly shows that Amun does not approve of lying, and that lying is worthy of not being able to make it into the Duat. Lying can be likened to Apep. Apep, God's enemy, is also known as the Uncreated One and his actions are known to go against Ma'at and "Uncreate" as it were, the creations of Amun. This of course is not good or approved by Amun. Lying, in a way, is like Uncreating to truth that you know is in your heart and mind. And Amun is a God of truth. Therefore, intentionally telling an untruth is as despised by Amun as Apep.