만이 만을 만에

who can tell me how to use these and why it is sometimes necessary and sometimes not to add 를, 이 or 에 after 만

원희만을 사랑한다

최고의 외국어 능통자만이 국제 연합의 통역사가 될 수 있다

My Opinion,
Without those particles, they all will make sense, meaning, they can be used to emphasize "만".


\^o^/

이, 을, 에게 are nominative, accusative and dative case marking particles and they may be omitted in the same way as they are omitted without 만.

Generally in colloquial style, case marking particles are often omitted. The omission is not considered as grammatically wrong when the case of the noun in the phrase is obvious without the particle. When a case marking particle is composed with a supportive particle (adding a meaning)만, the former is often omitted even in written style. The phrase becomes more airy, less heavy.

Generally, the case marking particle 이, 을, 에게 should not be omitted when the phrase is the response to a question with “Who”, “Whom”, or “to whom” respectively. However when 만 is used 이, 을, 에 can be omitted even though the phrase is the response to a question “Who”, “Whom”, or “to whom”. In that case using 이, 을, 에 just put accent on “Who”, “Whom”, or “to whom”.

만이 만을 만에

who can tell me how to use these and why it is sometimes necessary and sometimes not to add 를, 이 or 에 after 만

원희만을 사랑한다 \

I love only Wonhee.

최고의 외국어 능통자만이 국제 연합의 통역사가 될 수 있다

Only the person, who is good at foreign language, can become an interpreter for National institution.:)

이해하길 바라면서 영어로 작문해 보았습니다.