Sameer Maheshwari is the ideal boyfriend. But let's not forget the heartbreaks people suffered due to him.
Kamya -Perhaps the first girl who suffered heartbreak from Sameer. Kamya was instantly smitten by the charm and looks of Sameer, just like many others girls. Having extreme faith in her own beauty and charms, she didn't take much time to propose to him. However, to her dismay, Sameer expressed his love for a girl more beautiful than her, both inside and out (reference to Julia Roberts). He straightaway refused her advances and walked away.
She still however flirted with him and tried to come close to him until she finally joined the dots and realised his intense and unconditional love for Naina, following which she became a supporter of their love and acted as a pillar of support when their love suffered separation
Swati- Being an extremely romantic and filmy girl, Swati instantly became besotted with the handsome Sameer. It was more like love at first sight for her and she developed an instant crush on him. To fainting on seeing him arrive on bike, or becoming disappointed on not getting a kiss in school play, she openly displayed her love. However, she soon overheard Sameer expressing his love for a girl and became heartbroken. She still however moved on and tried to resist his charms, until she came to know about the relationship between her first love and her bestfriend. On learning the truth, she felt betrayed and broke off her friendship with Naina, until Sameer had finally put some sense into her, following which she supported Naina and her love for Sameer and became an active member of anti Sameer gang , on learning the truth. She even advised Naina against trusting Sameer blindly, when she came to know about his past relationship in Nainital.
She still however carried the grudge of not being able to be with Sameer due to Naina, something which she shared with Sunaina when her childhood friendship was falling apart.
Naina- Being a studious, innocent and introvert girl, the concept of first love was unique for Naina. She instantly fell for Sameer on seeing for the very first time and believed him to be the 'one'. However, the open display of affections by other girls and repeated confession of love for Sameer by Swati, she tried to push her feelings aside. She still however thought of ways to be close to him. She did things which she had never done before- knitting a sweater, going to his birthday party and most importantly lying to save him. She did push aside her morals on more than one occasion to save him. All these things made her heartbreak even more painful since she believed that Sameer wold never break her trust, not knowing that her with him relationship was built on a bet. Post the relevation, her heartbreak landed her in hospital, where she realised the importance of her happiness for her family. She changed into a heartless person( ruthlessly rejecting Sameer's love and repeated apologies) and decided to change back to her usual old self ( one who concentrated on her studies and her family ) . However all these attempts at forgetting Sameer proved futile, since her unconditional love did overpower her strong will. Little did she know that she had just became the lifeline of hero Sameer Maheshwari.
Sunaina- Similar to Kamya and Swati, she was immediately besotted with the handsome Sameer. She tried her best to be close to him and steal glances. Supported by the Samaina gang, she proposed to Sameer, believing he was interested in her. However, she got her answer after a long time, in the form of Sameer's rebound. He proposed to her in front of whole college, shared his heartbreak with her , asked for her help in forgetting Naina, held her hand, took her on bike ride and openly displayed his fake love. However, little did she know that all this was just to make his ladylove jealous and get her back. When Sameer realised his mistake and got a chance to be back with Naina(as a friend) , he became indifferent to sunaina( snatching his hand away and walking out) and immediately broke off things with her. He even confessed that he was never in love with her and all this was just to get Naina back, making her heartbreak even more painful. She walked out faking a smile. She still however hoped that after Naina's marriage, Sameer will realise her worth and will come back to her(as she shared with Mitali). After all her hopes were shattered and Naina and Sameer reconciled, she switched to vamp mode and decided to take her revenge from Sameer by giving pain to the person he loved the most- his Naina.
That is perhaps the main difference between Naina and Sunaina. While post her heartbreak, Naina concentrated on studies and avoided Sameer ( harbouring no feelings of revenge from him), Sunaina became a completely different person and went to extremely low levels, even toying with the true love of Kartik.
So is the difference in Sameer's apology. He spent a night sleeping on road, secretly gave a cycle to Naina and apologized to Rakesh -- for forgiveness from his ladylove( while he was unaware of his feelings for her and still considered her a dear friend). But with Sunaina, he believed that a single 'sorry ' will do wonders and she will forgive him, showing just how little she and her heartbreak meant to him.