So I've been doing a lot of thinking and have read a lot of threads/ posts about Viren doing this only for revenge... most of the posters have been NivArth fans who refuse to accept NivRen as a jodi but now I see my own friend Rachna, who being a NivRen fan, can't accept that Viren loves Nivi and meant what he said to her.
I've done a lot of thinking and have analyzed his character time and time again to only come to one conclusion.. Viren is not the kind of guy who lies about love even if it is to get revenge at his enemy. I feel like everything he said is sincere and straight from his heart... (mind you this is only my opinion with reasons which I am not trying to force on anyone, nor am I trying to bash the ideas of other parties-- and although I may be wrong, at this point I don't believe I can be wrong)... anyways, Viren has seen Nivi and the way she is. He's seen who Nivi is and the way she acts and holds herself in front of others.
You guys know the phrase, the first impression is the one that lasts forever? Well if you remember Viren's first impression of Nivi, it was of a helpless girl who would do anything to try to save her father. And mind you, he thought of her as helpless not because she could not do for herself but because she needed help to try to fight the world. From the first moment, he knew with her passion for saving her dad, that was something she could do for herself and so he didn't have a problem with leaving Keshav in her hands.
Then Nivi and Viren met more and more and Viren gradually saw who Nivi is before even realizing that she is his enemy's daughter. If we recap to previous scenes, for example the Mandir scene, Nivi told him that she was not only praying for her father but someone else close to her and after that she also told him that she would pray that his brother understands the value of family. So from that he could see how much of a caring girl she really is as she was hoping for the best for his family when she didn't even know who his family is. Also another scene, when Viren was telling her he has an enemy, she was like don't hate someone so much as it turns out to be worse for you than that person. From these meetings and the numerous other ones that NivRen have had even before knowing each other's real identities, Viren has an idea of who this girl is.
As for when he found out that she was the enemy's daughter... he was shocked as he should be and he was mad because his enemy's daughter was right before him and he never knew but then he questioned it. He thought to himself how could THIS girl be the enemy's daughter.. how could this girl cause my family so much pain. At that point he has a clear idea of how Nivi is and he couldn't grasp such an idea that she could cause so much problems in his family and be the reason behind his grandfather's current health condition.
So this brings me to the meetings AFTER he found out that she was Nivedita Sharma, Keshav Sharma's (also known as his dushmaan's) daughter. Even after he knew she was his enemy's daughter, he told her not to cry as if you cry then God and the universe will give you reason to cry. He never once attempted to hurt her or make her feel bad the way he did with Divya when he mistook her for the "dushmaan ki beti".
Now let's look at what Viren has done that shows that him saying I LOVE YOU NIVEDITA not something he would do out of revenge...
let's look at the episode where he put the powder into Nivi's drink.. he only did that to find more out about her and also because he knew how tired she was and how she needed rest before she made herself sick. Fine, you guys have doubts about that and can't believe that his only motif was to find out more about her. But then why would he decorate the whole house while she was asleep? Don't say it was cause he wanted the house to be decorated in time as it his brother's wedding function because if that was the case then he wouldn't have hid the fact that he paid 20 extra workers (from his pocket) to finish the work and that he handled it all. He would have taken the credit but he didn't.
Now let's fast forward to this last episode where he said that he loves her. Now you guys are questioning how could he love her so quickly. But what you guys tend to neglect is how could he not? Nivi's character is someone you can fall in love with easily because of how beautiful and caring she is on the inside. How she just wants the better for everyone. Fine, this doesn't convince you. Then let's look at what he did today. If Viren wanted revenge, then why didn't he let the wooden log hit Nivi? Why was there that scared/ worried look on his face as he saw the closet shaking and the wooden log about to fall? If you say cause he wanted revenge on a bigger scale, then her getting hurt wouldn't matter cause he's want to take revenge as many ways possible. Now look at his words. The things he said to Nivi were straight from his heart. The pain in his eyes was pain because she was rejecting him and that's what everyone is scared of.. rejection. No one wants to fall in love and not recieve that love in return. Viren loves Nivi as it is so transparent in his words and in his eyes.
But if you still doubt me, then we just have to wait and watch as the story unfolds.