Hi guys,

Would you please translate the following for me? in a joking/friendly way?

"bet it's killing you softly"

many thanks!

koala

If you're referring to the song "Killing me softly with his song" and you want to make a joke about it in Japanese based on a play of words I'm afraid your joke may be lost in translation. The song is known in Japanese as [url="http://ja.wikipedia.org/wiki/%E3%82%84%E3%81%95%E3%81%97%E3%81%8F%E6%AD%8C%E3%81%A3%E3%81%A6]やさしく歌って[/url], meaning "Sing gently".

You could still translate "killing you softly" directly into Japanese but they'll probably have no clue what you're referring to. Just to throw something out there, let's say:
あれで、やさしく殺されているんじゃないか。
The phrase could sound differently depending on male/female/relationship/etc nuances (Japanese sounds differently depending on who's talking to whom).

This is very hard to do; the phrase is very idiomatic in English and I'm not even entirely sure what it means (in English) since there's no context. Do you just want to express the idea that it's "eating him up inside" or something like that?

The translation given above is literal and grammatically correct, but it's not likely to do much more than confuse a Japanese person.