Verbseoul.
하다 verb (adj)
야비하다yabihadato be base, to be mean, to be underhanded

To say to be base, to be mean, to be underhanded politely in the present tense, use 야비해요 (yah-bee-hae-yoh). Below is the full conjugation of 야비하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
야비해
yah-bee-hae
야비해요
yah-bee-hae-yoh
야비합니다
yah-bee-hahm-nee-dah
Past
야비했어
yah-bee-hae-ssuh
야비했어요
yah-bee-hae-ssuh-yoh
야비했습니다
yah-bee-hae-sseum-nee-dah
Future
야비할 거야
yah-bee-hahl- -guh-yah
야비할 거예요
yah-bee-hahl- -guh-yae-yoh
야비할 겁니다
yah-bee-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
야비하세요
yah-bee-hah-sae-yoh
Suggestion / Let's Polite (요)
야비해요
yah-bee-hae-yoh
Question Polite (요)
야비해요?
yah-bee-hae-yoh-?
Connective “and” — (고)
야비하고
yah-bee-hah-goh
Conditional “if” — (면)
야비하면
yah-bee-hah-myuhn
Noun form — (기)
야비함
yah-bee-hahm