나는 너를 좋아합니다.
nanun norul joahamnida (formal)
나는 너를 좋아해요.
nanun norul joaheyo (informal)
나는 너를 좋아해.
nanun norul joahe. (intimate)
but, in Korean, subject and object are not that important so it's actually better to just drop them and say:
좋아합니다 or 좋아해요
(joahamnida) (joaheyo)
Suwertehin ka sana ^^