Verbseoul.
하다 verb
망하다manghadato fail, to go under

To say to fail, to go under politely in the present tense, use 망해요 (mahng-hae-yoh). Below is the full conjugation of 망하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
망해
mahng-hae
망해요
mahng-hae-yoh
망합니다
mahng-hahm-nee-dah
Past
망했어
mahng-hae-ssuh
망했어요
mahng-hae-ssuh-yoh
망했습니다
mahng-hae-sseum-nee-dah
Future
망할 거야
mahng-hahl- -guh-yah
망할 거예요
mahng-hahl- -guh-yae-yoh
망할 겁니다
mahng-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
망하세요
mahng-hah-sae-yoh
Suggestion / Let's Polite (요)
망해요
mahng-hae-yoh
Question Polite (요)
망해요?
mahng-hae-yoh-?
Connective “and” — (고)
망하고
mahng-hah-goh
Conditional “if” — (면)
망하면
mahng-hah-myuhn
Noun form — (기)
망함
mahng-hahm