You can try to permanently exterminate them and fail. Additionally, even if you succeed in one case, you will ensure that no one else will be willing to negotiate with you even when it would be beneficial for you because they are stronger. So overall you will be decreasing your options, which makes your situation worse.
If the alternative to negotation is completely exterminating you enemies, you don’t have to worry about permanent enemies!
You can try to permanently exterminate them and fail. Additionally, even if you succeed in one case, you will ensure that no one else will be willing to negotiate with you even when it would be beneficial for you because they are stronger. So overall you will be decreasing your options, which makes your situation worse.