Verbseoul.
하다 verb
실망하다silmanghadato be disappointed

To say to be disappointed politely in the present tense, use 실망해요 (sheel-mahng-hae-yoh). Below is the full conjugation of 실망하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
실망해
sheel-mahng-hae
실망해요
sheel-mahng-hae-yoh
실망합니다
sheel-mahng-hahm-nee-dah
Past
실망했어
sheel-mahng-hae-ssuh
실망했어요
sheel-mahng-hae-ssuh-yoh
실망했습니다
sheel-mahng-hae-sseum-nee-dah
Future
실망할 거야
sheel-mahng-hahl- -guh-yah
실망할 거예요
sheel-mahng-hahl- -guh-yae-yoh
실망할 겁니다
sheel-mahng-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
실망하세요
sheel-mahng-hah-sae-yoh
Suggestion / Let's Polite (요)
실망해요
sheel-mahng-hae-yoh
Question Polite (요)
실망해요?
sheel-mahng-hae-yoh-?
Connective “and” — (고)
실망하고
sheel-mahng-hah-goh
Conditional “if” — (면)
실망하면
sheel-mahng-hah-myuhn
Noun form — (기)
실망함
sheel-mahng-hahm