What would you say if you are asked なっとうがすきですか (do you like nattou?)?
If you like it, then you can of course say.
はい、すきです。(hai, suki desu / Yes, I like it)
or
はい、だいすきです。(hai, dai_suki desu / Yes, I love it.)
If you don’t like it, you can say:
いいえ、すきじゃないです。(iie, suki_janai desu / No, I don’t like it.)
But いいえ、きらいです。(iie, kirai desu / No, I dislike it.) or いいえ、だいきらいです。(iie, dai_kirai desu / No, I hate it.) does not really sound diplomatic.
If you really don’t like “nattou”, the most diplomatic response is:
いいえ、なっとうはにがてです。(iie, nattou wa nigate desu.)
“いいえ、xxx は にがて です。(Iie, xxx wa nigate desu.)” means “I have an aversion to xxx” and it does not sound too personal.
If you are volunteering the information without being asked, you can say:
わたし は xxx が にがて です。(watashi wa xxx ga nigate desu.) – note the particle change.
This “nigate” is the opposite of とくい (tokui / confident in), so if you are not good at tennis, you can also say:
（わたし は）テニス が にがて です。
