If "negotiate" means to discuss and reach an agreement:
* Refuse: To decline to discuss or agree.
* Demand: To insist on something without compromise.
* Dictate: To impose terms without discussion.
* Fight: To engage in a conflict instead of negotiating.
* Break off: To end negotiations abruptly.
If "negotiate" means to manage or handle a situation successfully:
* Fail: To be unable to manage or succeed.
* Botch: To handle something poorly or ineptly.
* Worsen: To make the situation worse.
If "negotiate" means to make a deal or bargain:
* Reject: To refuse to accept a deal.
* Walk away: To leave a negotiation without an agreement.
* Oppose: To be against the terms of a deal.
If "negotiate" means to move or maneuver carefully:
* Crash: To move with force or without caution.
* Force: To use force or pressure instead of careful movement.
To give you the best antonym, please tell me how you are using the word "negotiate" in your context.