Answer:
Passionless
Unpassionate
Unenthusiastic
Explanation:
All these words show up when you do a search about the antonym of Passionate. Someone who has passion is a passionate person. A person who is "showing or caused by strong feelings or a strong belief."
Passionless and Unpassionate both mean someone who lacks passion.
Unenthusiastic means: "having or showing a lack of excitement or enthusiasm"
