1Disappointment — the feeling of being let down or losing hope when something expected doesn't happen; can be used as a verb with 'suru.'
テストの結果に失望したが、次はがんばろうと思った。
I was disappointed by my test results, but I decided to do better next time.
楽しみにしていた旅行が中止になり、みんな失望を隠せなかった。
The trip we had been looking forward to was cancelled, and everyone couldn't hide their disappointment.
彼の無責任な発言にファンは失望した。
Fans were disappointed by his irresponsible remarks.
結果はどうであれ、失望する必要はない。
Whatever the result, there's no need to be disappointed.