I totally agree with you.
我完全同意你的看法。
I am 100% behind you.
我百分之百地支持你。
Yes, I am with you.
是的，我同意你的看法。
I couldn't agree more.
我完全同意。
I think you argued your case extremely well.
我认为你的论据十分具有说服力。
I think it is difficult to make a case against you.
我认为很难提出充分的理由反对你。
I think I will make a case for you.
我想我会支持你。