Shortly afterwards, she was cast for the first time as a villain in the thriller Fida. The film follows the story of an on-line robbery and the Mumbai underworld with which her character Neha Mehra becomes involved. During the filming of Fida, Kapoor entered into a relationship with actor Shahid Kapoor, whom she later described as having "a major positive influence in my life. Although the film did not succeed at the box office, Kapoor garnered positive reviews for her performance, with some critics noting a distinct progression from her earlier roles. Her subsequent releases that year included Abbas-Mustan's moderately successful thriller Aitraaz and Priyadarshan's comedy Hulchul, her first box office success since 2002.In 2005, she starred as the protagonist in Bewafaa, a drama directed by Dharmesh Darshan. The feature received mostly negative reviews and Kapoor's portrayal of Anjali Sahai, an unfaithful woman, was not well-received. Nikhat Kazmi of Indiatimes believed that in an effort to become a serious actress, Kapoor was embodying a maturer, more jaded character ahead of her years in Bewafaa which appeared peculiar for a young woman of her age. Later that year, she appeared in Priyadarshan's romantic drama Kyon Ki, which was set in a psychiatric hospital, and relates the love story of a mentally ill patient, played by Salman Khan, and his physician, played by Kapoor. The film was a box office failure though Kapoor's performance was generally enjoyed by critics, with the BBC reporting, "It goes without saying that she is a pure natural when it comes to acting. Kapoor then was cast in the romance Dosti: Friends Forever. While not a success in India, the film became the highest-grossing Bollywood film of 2005 in the United Kingdom
"Kareena is an apt Desdemona to Ajay Devgn's Othello. As young Dolly who elopes with a man she is madly in love with and ultimately becomes a victim of his violent jealousy, Kareena is brilliant. Her vulnerability is palpable, her expression of love endearing Kareena internalises her character with stupefying intelligence and throws up a performance that leaves you overwhelmed. And she makes it look so effortless."Filmfare on Kapoor's performance in Omkara (2006In 2006, Kapoor appeared in three films. She first starred in the thriller 36 China Town followed by the comedy Chup Chup Ke; both films performed reasonably well She next portrayed the Shakespearean character of Desdemona in Omkara, the Hindi adaptation of William Shakespeare's Othello. Directed by Vishal Bhardwaj, the film is a tragedy of sexual jealousy set against the backdrop of the political system in Uttar Pradesh. The film premiered at the 2006 Cannes Film Festival and was also selected for screening at the Cairo International Film Festival Omkara was embraced by critics and Kapoor's portrayal earned her a fourth Filmfare Award and first Star Screen Award; her performance was later included in the 2010 issue of the "Top 80 Iconic Performances" by Filmfare. Kapoor herself considers her role in Omkara as a "new benchmark" in her career and has made comparisons between her portrayal of Dolly and her own evolving maturity as a woman.
Following Omkara, she stopped acting for a short time, as she felt that "nothing [was] challenging enough for me to say yes In an interview with The Times of India, Kapoor commented, "In my initial years in the industry, I pushed myself to do a lot of work because I was greedy. I did some films which I now regret – purely for the money. Today, I want to do selective filmsShe later described this period as a way to "relax and unwind" herself
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