He's not evil per say. He's just extremely arrogant and just cannot think beyond himself. He's willing to put anyone through any level of trauma to satisfy his own ego and his own desires. Forget Preeta. His own family is unhappy with him but he still believes he shouldn't change one bit. And Preeta's response to him sort of shows she's okay with his dominating behaviour. Maybe she's a submissive. Who derives pleasure from pain. š¤¢@bold..... true. his smile was very strange. i really got confused what is he smiling at. he really seemed evil at that time. they have really turned karan into a grey shaded lead. or should i say 'dark grey'. someone like maya from beyhadh season-1 (minus murders). he is a grey shaded anti-hero lead character in true sense.
but remember arjun ended up with saanjh. not maya. though maya was the lead.