I am not comfortable with your idea.
我對你的想法感到不舒服。
I don't think your plan is realistic.
我認為你的計劃不現實。
You fail to convince me.
你沒有說服我。
I am not convinced about that.
我不確信這一點。
I totally disagree.
我完全不同意。
I am against your suggestions.
我反對你的建議。
I couldn't agree less.
我完全不同意。
I must disagree with you.
我必須反對你。