Abhay Deol as Kabir Dewan in Zindagi Na Milegi Dobara was everyone's favourite. He was nice, tried his hardest to bring his friends back together, and was pushed around by his 'bully' of a girlfriend. Who, now that we look back, was also a victim of her boyfriend's indecisive nature.
Because let's be honest, their relationship was toxic. And Kabir needs to be blamed equally for that.
In the first scene, when he shows Natasha his ring, she misunderstands him and gets carried away. Which is not a surprise considering that they were both in a serious committed relationship. He should have known better than to show her a ring without context.
But did Kabir have the courage to tell her later that he didn't want this? Did he tell the person he loved that he wasn't ready and needed more time? The second Natasha questioned his intentions towards their relationship, he yielded and began pretending that he wanted this too.
Instead of facing his problems, he took a vacation with his friends to get his mind off things and then broke things off with Natasha because she was invested in their wedding, and he wasn't. Because, well, he didn't actually want to get married. He found looking at wedding invites boring, got so carried away with his bachelor party that he forgot why it was happening in the first place.
Because he wasn't mentally and emotionally prepared for the wedding, the idea of compromise and priorities becoming different, scared him.
But should Natasha alone be blamed for the downfall for their relationship? That seems a tad bit unfair. Kabir made the mess that inevitably came back to bite him in the ass. And it was satisfying to watch, because he didn't deserve to marry Natasha if his heart wasn't into it.