If you're disappointed at a person say: - "Are you crazy?" (sort of light hearted) - "You're unbelievable.." (kind of rude) If you're disappointed at a situation say: - "just my luck..." - "typical..." - "go figure" - "perfect..." (irony)

Here are a few more. Directed towards a person: "I do not know what I am going to do with you!." (It can be rude or not, depending on/of the actions of the person saying it and also the tone of their voice, but that should go without saying.) "Where in the world did you come up with that idea!?"(This one, I think needs to be expressed with actions and tones that indicate that you are upset with that person, because if not, it would be a literal statement)(Also, this is a rhetorical question, meaning it is stated as a question, but it is only to make a point) "Why in the world did you do that!?"(Here again, this one is exactly like the one above including that it is a rhetorical question) "Whatever!" (I think this one is a good it can stand completely on it's own, you could say this and then walk away or keep saying it until the other person shuts up, walks away, or starts to reason or console you) (Basically, it wants to say that "you just do not care") Directed towards a situation: "Oh man!" (After this usually you would go into the explanation of why you are upset about the situation and also it needs the actions and the tone to support it) "Great!" or "This is great!"(same as above) "This is not cool" (I think it can stand alone or you can elaborate further)(It is a little embarrassing, but I use this one often" "Crap" (Can stand alone or not) También quiero decir que estoy de acuerdo con las otras respuestas.

Just to answer one of your initial comments saying 'I am disappointed with you/I am disappointed in you' is not impolite.