I am not comfortable with your idea.
我对你的想法感到不舒服。
I don't think your plan is realistic.
我认为你的计划不现实。
You fail to convince me.
你没有说服我。
I am not convinced about that.
我不确信这一点。
I totally disagree.
我完全不同意。
I am against your suggestions.
我反对你的建议。
I couldn't agree less.
我完全不同意。
I must disagree with you.
我必须反对你。