Answer
The antagonist in the James Bond film "You Only Live Twice" is Ernst Stavro Blofeld, the enigmatic mastermind behind the villainous organization SPECTRE. Blofeld, known for his distinctive scarred face and fondness for cats, orchestrates a series of complex schemes aimed at world domination and seeks revenge against Bond for thwarting his previous plans. His cunning intellect and ruthless nature make him a formidable adversary for the British secret agent.