The antonyms for the word "most warm-hearted" can be described as cold, unkind, unfeeling or indifferent. Someone who lacks warmth in their personality or behavior is often seen as unfriendly, distant, or unapproachable. They may be insensitive to the needs of others or lack empathy in their actions or words. A person who is cold-hearted may seem uninterested in developing meaningful relationships or showing compassion towards others. In contrast to someone who is warm-hearted and kind, a cold-hearted person may seem callous, unemotional, and selfish. Therefore, it is important to cultivate warmth and kindness in our interactions with others.