Ramachandran's breakthrough came with his first lead role in A. S. A. Sami's swashbuckler film "Rajakumari" (1947) where he played a villager who marries a princess. Based on the "Arabian Nights", "Rajakumari" was a commercially successful venture. He established himself as an action hero akin to Errol Flynn and Douglas Fairbanks in Tamil cinema with "Manthiri Kumari" (1950) and "Marmayogi" (1951). Both films had political undertones which earned Ramachandran a Robin Hood persona of being a champion for the downtrodden. His performance as the caring brother Rajendran who tries to keep his family together in "En Thangai" (1952) earned him critical acclaim. In 1953, he made his debut in Malayalam films opposite B. S. Saroja in "Genova". Ramachandran continued to play roles which enabled him to adopt his ideas of fighting injustice meted out to the poor such as an outlaw in "Malaikkallan" (1954), and "Nadodi Mannan" (1958). In the latter, he featured in dual roles, as a king and a commoner, for the first time in his career. Both "Malaikkallan" and "Nadodi Mannan" were commercially successful, becoming the highest-grossing films of their respective release years. In addition to social dramas, Ramachandran received positive feedback and commercial success for fantasy swashbuckler films such as "Alibabavum 40 Thirudargalum" (1956), the first South Indian full-length colour film, "Madurai Veeran" (1956), "Chakravarthi Thirumagal" (1957), and "Mahadhevi" (1957).