The CVs have left it to the viewers to guess the reason and accordingly, my take is that Kuki, his babygirl for whom Bajaj had lived till now & is his entire world, stopping him furiously from holding her, was the biggest punishment he would have got in his lifetime and he being at the mercy of Pre to get back his daughter both by donating blood & by making her understand that apart from her there was noone for her Dad, was the biggest revenge anyone could give him.
Why i believe so is because, instead of showing a shocked Kuki who gets frightened seeing her Dad who hours back was about to kill her Mom, what we got was a furious Kuki who didn't want to talk to or even touch him because he hurted her Mom. And that was purposely shown for two reasons. First, to let Bajaj realise the pain of being distanced from the one you love, eventhough it was for a short time. Who knows, if the channel had not interfered, Kuki ignoring her Dad would have been extended for some more days to show Bajaj experiencing that pain Pre went through. Second reason was to bring everything to a full circle. This track started when Pre went to BM after seeing Mohini's tears and promising her to bring back her son. And the track ends with the same Pre being the reason of making Kuki realise how important she is to her Dad & why she should be back with him. In short, Bajaj who exploited the vulnerable moments & emotions of 2mothers to get a mother for his child had to go through the same emotions of a parent to realise his mistake and who better than Kuki, the reason for this deal marriage, can make him realise where he went wrong.
So, those who feel that Bajaj is left unpunished, it is not the truth. It is just because of the overnight script changes and lack of time probably due to channel interference, that the message could not be easily conveyed because of lack of drama related to the same. Hence, AnuPre lovers, please chill and try to spread positive vibes.