2007 proved to be Kumar's most successful year during his career in the industry, and as described by box office analysts, "probably the best ever recorded by an actor, with four outright hits and no flops." His first release, Vipul Amrutlal Shah-directed Namastey London, was critically and commercially successful, and his performance earned him a Best Actor nomination at the Filmfare. Critic Taran Adarsh wrote of his performance in the film, "he's sure to win the hearts of millions of moviegoers with a terrific portrayal in this film." Kumar's chemistry with lead actress Katrina Kaif also generated immense appreciation, with Nikhat Kazmi of The Times of India describing their pairing as "refreshing." His next two releases, Sajid Khan-directed Heyy Babyy and Priyadarshan's Bhool Bhulaiyaa, were box office successes as well. In both of these films he starred opposite Vidya Balan. Kumar's last release of the year, the Anees Bazmee-directed Welcome, did extremely well at the box office, receiving a blockbuster status and simultaneously becoming his fifth successive hit. All of Kumar's films which released that year did well in the overseas market as well. Kumar appeared in a cameo role in Farah Khan directed Om Shanti Om. His role was listed as no. 3 on the Top 10 Cameos in Bollywood list of MensXP.com.Kumar's first film of 2008, Vijay Krishna Acharya-directed action thriller Tashan, marked his comeback to the Yash Raj Films banner after 11 years. Although a poll (conducted by Bollywood Hungama) named it the most anticipated release of the year, the film under-performed at the box office grossing ₹279 million (US$4.0 million) in India. His second film, Bazmee-directed Singh Is Kinng in which he starred opposite Kaif was a huge success at the box office and broke the first-week worldwide record of Om Shanti Om, the previous highest figure. His next film was the animated film Jumbo, directed by Kompin Kemgumnird. The year also saw Kumar making his small screen debut as the host of the successful show Fear Factor – Khatron Ke Khiladi. He later returned to host the show's second season in 2009.In 2009, Kumar featured opposite Deepika Padukone in the Warner Bros. and Rohan Sippy production Chandni Chowk to China. Directed by Nikhil Advani, the film was a critical and commercial failure at the box office. Kumar's next release was 8 x 10 Tasveer. Directed by Nagesh Kukunoor, the film was a commercially failure however Akshay Kumar won the Stardust Best Actor Award for his controlled and restrained performance. His next release was Sabbir Khan's battle-of-the-sexes comedy Kambakkht Ishq. Set in Los Angeles, it was the first Indian film to be shot at Universal Studios and featured cameo appearances by Hollywood actors. The film was poorly received by critics but became an economic success, earning over ₹840 million (US$12 million) worldwide. Kumar's film Blue was released on 16 October 2009. Blue received negative reviews and collected about ₹ 420 million at the box office. His last release in 2009 was Priyadarshan's De Dana Dan. He starred alongside Katrina Kaif, Suniel Shetty and Paresh Rawal. Kumar played a servant who plans to kidnap his owner's dog. The film received mixed reviews.He then appeared in the 2010 comedy, Housefull, directed by Sajid Khan which garnered the second-highest opening weekend collection of all time. Kumar's next release was Khatta Meetha, directed by Priyadarshan which was an average grosser. The film received negative reviews. Rajeev Masand of CNN-IBN called it a schizophrenic film.

Question: What is the most successful year for Kumar in his career?
Answer: 2007