对……失望be disappointed about;be disappointed at;对某人失望be disappointed with sbdespair n. 绝望, 失望, 令人失望的人(事物) vi. 绝望 handwringing n. 绝望, 歇斯底里状态 adj. 绝望的 throw up one's handsv. 绝望
我对你很失望有以下几种翻译。I am very disappointed with you.(这是最常用的表达方式吧)I hold out no hope of you.(这是我套用有道词典上的用法)You let me down to a large degree.(这个貌似有点高级)不确定能否对你有帮助,希望你权衡采纳,谢谢。