The phrase "most red-blooded" refers to someone who is extremely passionate or enthusiastic. However, antonyms for this phrase could include "apathetic," meaning lacking interest or emotion, or "unenthusiastic," meaning lacking excitement or passion. Another antonym could be "stoic," referring to someone who is calm and unemotional. Alternatively, "indifferent" could be used to describe someone who is neutral or unbiased in their feelings towards a particular topic. Therefore, while being "most red-blooded" might connote enthusiasm and energy, its antonyms invoke a sense of detachment and disinterest.