Why does Duncan feel he is guilty of ingratitude toward Macbeth

As Macbeth goes to war despite of him and brings him victory.

Explanation:

In Act one, scene four, Macbeth conquers all the enemies of Duncan. So he was so much happy and feels that even he cannot bring this much victory to his kingdom but Macbeth does. Hence he says that he is feeling guilty of ingratitude through he gave Macbeth "The Thane of Cowdar". Duncan feels this is not worthy when compared to his victory and hence he feels guilty of ingratitude.