I'd like to express my disappointment.

Meaning

I'm unhappy with...

Examples

• John: Is everything alright?
• Alice: No, actually. <b>I'd like to express my disappointment</b> with the service.
• John: Oh dear, what happened?
• Alice: The food was cold and the waiter was very rude. <b>I'd like to express my disappointment</b> formally in writing as well.