Antonyms for the expression "buddy buddy" could be distant, unfriendly, hostile, or antagonistic. Buddy buddy means someone who is close and friendly with others, but distant is completely opposite to it, meaning remote or detached. Unfriendly is someone who doesn't initiate a conversation and doesn't participate in any activities, opposite to buddy buddy. Hostile is someone who is actively against or opposed to others, and it is the opposite of friendly. Lastly, antagonistic is used to describe someone who is aggressive or confrontational towards others, and it is completely opposite to buddy buddy.