Verbseoul.
ㄹ stem (adj)
모질다mojildaharsh

To say harsh politely in the present tense, use 모질어요 (moh-chee-ruh-yoh). Below is the full conjugation of 모질다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
모질어
moh-chee-ruh
모질어요
moh-chee-ruh-yoh
모집니다
moh-cheem-nee-dah
Past
모질었어
moh-chee-ruh-ssuh
모질었어요
moh-chee-ruh-ssuh-yoh
모질었습니다
moh-chee-ruh-sseum-nee-dah
Future
모질 거야
moh-cheel- -guh-yah
모질 거예요
moh-cheel- -guh-yae-yoh
모질 겁니다
moh-cheel- -guhm-nee-dah

Other useful forms

Command Polite (세요)
모지세요
moh-chee-sae-yoh
Suggestion / Let's Polite (요)
모질어요
moh-chee-ruh-yoh
Question Polite (요)
모질어요?
moh-chee-ruh-yoh-?
Connective “and” — (고)
모질고
moh-cheel-goh
Conditional “if” — (면)
모질면
moh-cheel-myuhn
Noun form — (기)
모짊
moh-cheem