The phrase "changed heart" refers to a deep transformation or shift in one's beliefs, feelings, or intentions. Some possible antonyms for this phrase could be "hardened heart," "unchanging heart," or "stubborn heart." A hardened heart implies someone who is closed off to new ideas or experiences, whereas an unchanging heart suggests someone who is set in their ways and resistant to change. A stubborn heart connotes someone who is unwilling to compromise or listen to others' perspectives. It's important to note that these antonyms are all subjective and depend on the individual's perception and interpretation of the phrase "changed heart.