Amongst the 5, DT got my vote...
PhoolChand, as we all know, is a complete duffer😆 And to some extent we cannot really call him a villain because his harkata somehow always manage to bring ViDha closer😉
Dulaari is more of an anti-hero type than an actual villain. She strictly follows rules and customs but mainly she's just a very over-protective mother. We don't really know their background so even though she is very harsh, it is probably for good reason.
I actually appreciated TT when he wanted to plot against DT. Recently he's been really annoying, but at the very least somehow I feel that his love for his mother redeems him in a tiny tiny manner. In any case, for the most part of it, he follows more than he plots so he's not the top contender.
Kanak comes very close, but I feel that there are a few things that distinguish her from DT. The actress is fantastic at her role, and it's quite intriguing how the pitch of her voice changes when she is talking to DT vs Viplav (bechari maa). It is quite appaling how she disrespects her mother-in-law - but then again, she only follows from the one who leads. Even though she is often petty and very selfish, she still does most of her evilness out of concern for Viplav. Most of all though, she does not hide her nature (except from Viplav, but nobody tells him anything so he doesn't quite count😆). Whatever she is, she shows it quite clearly to people.
Which is why, DT is the best negative character of all. He hides himself so well that besides a handful few extremely loyal people who will never leave him, nobody else knows what his true nature is like. Not even Durga, in front of whom he shows a pretense to take advantage of her. Those who have known and were unfortunate enough to be caught never face a good consequence. DT is not only manipulative, he is also a cheat (as we saw when he sent Shalu's fiance away to evade tax fraud). He uses his position of power to control those around him - and he does not spare Viplav either. The way he talked badly about Viplav to Dhaani (that V stole the ashram papers) to make her suspect him, is not something I believe Kanak would do as she is very proud of her son. As DT leaves nobody in his quest for power, he is the worst of the worst.