These negotiations carry a strong adversarial tone.
Tips
grammar
敌对 (hostile, adversarial) + 性 (-ness / -ity). The -性 suffix turns an adjective into an abstract noun, like English -ity / -ness. Compare 重要性 (importance), 可能性 (possibility), 危险性 (dangerousness).
usage
Mostly appears in formal writing — international relations, legal arguments, sociology. In conversation you'd say 敌意 (díyì, 'hostility') instead.