The way Karthik handled all of Raghav's blows till now it is truly commendable. Fingers crossed for it to remain the same.
When Karthik saw Naira's photo in Raghav's wallet. He confronted Raghav about the matter even wanted to speak to Naira about it, but then other things were going on so decided to do it later on.
Raghav purposefully talking on the phone and then coming to the party in front of Karthik saying things like mein ne Tina ko hurt kiya and all. Karthik not once asked about the matter, he asked Raghav to leave as he is not important because if he was Naira would have mentioned about him.
These two weren't that big things, but getting a letter in your hand saying that your partner had another's child in their womb is huge. That too the letter is not directed to you, if it was, you could easily shrug it away thinking someone is trying to feed stuff into your mind, but this letter was an apology letter directed towards Naira, that Karthik got in his hands on. Still this guy has handled the situation so calmly and maturely. His whole focus is only on protecting Naira and get to the bottom of everything without getting Naira involved so she isn't hurt.
Karthik is the best partner a girl can wish.