The phrase "in right mind" refers to someone who is mentally sound and capable of making reasonable decisions. Antonyms for this phrase include "mentally unstable," "insane," "mad," "delusional," "illogical," and "irrational." These antonyms suggest that the person is not capable of thinking rationally and is potentially a danger to themselves or others. Other antonyms could include "unconscious" or "in a coma," which suggest that the person is not aware or conscious of their surroundings. However, it is important to note that using these antonyms in a derogatory or insulting manner can perpetuate harmful stigmas surrounding mental health.