Simple:
* The news of the cancelled concert was a huge disappointment.
* Her disappointment was evident in her voice.
More complex:
* Despite his disappointment, he managed to keep a positive attitude.
* The disappointment she felt at not getting the job was overwhelming.
* The team's disappointment was palpable after their loss in the final game.
Figurative language:
* The empty seat at the dinner table was a disappointment that hung heavy in the air.
* Her disappointment was like a lead weight in her stomach.
You can choose the sentence that best suits the context of your writing.