I believe himself...I think it was not so much about punishing Naku it was more about punishing himself. Agree Ani. Dutta has been the harshest on himself.
I also somehow believe that Dutta was trying to figure out Naku...why she did what she did and show her the monster in him...he felt he had let out...to see if she start hating him and if she start looking at him differently. Testing her out...may be he wanted to believe her in some corner of his mind when she declared her eternal love for him
All the punishment he was giving Naku...if we look at it from Dutta's view...then I believe we will realize...that it had more to do about what he felt about himself and punishing himself than Naku.
Of course he was hurting and very angry at Naku...but he was more angry at himself for trusting her...for believing in what dream she was showing him could turn out true...for believing in that what she said she saw in him and the way she saw him...he would see himself the way too.😊 Wonderfully analyzed and explained, Ani 👏