https://www.proz.com/kudoz/japanese-to-english/other/56687-kibunwarui.html

Proposed translations

7 mins
Selected

Feeling bad

Assuming the subject is "I" (depending on the context you will have to judge who the subject is), "kibun warui" means "I feel unwell/ill/sick/indisposed/seedy". It can also be translated as "be out of sorts", "do not feel oneself" or "be poorly".
Peer comment(s):

pds : Yes, depends somewhat on the context
22 mins
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4 KudoZ points awarded for this answer.
6 mins

feel sick, feel bad

feel sick, feel bad
Peer comment(s):

ProZ.com Staff : said alone, it probably means "I feel bad"
4 mins
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7 mins

feel sick, feel ill, unwell

It normally "kibun ga warui" meaning " I don't feel well."
Reference:

Ten years in Japan

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31 mins

I don't feel so good

Depending on the context it can mean anywhere between

I don't feel so good

and

I feel really sick.

When no subject is indicated, it is probably the first person singular
Peer comment(s):

Maynard Hogg : e.g. motion sickness "I don't feel so good"
18 hrs
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1 hr

I don't feel well, I feel unwell, I feel sick, I feel bad ...

Depending on context (?), 気分が悪い (kibun ga warui) means : "I feel bad, I don't feel well, I feel unwell, I feel undisposed, I feel sick, etc."
I think that originally this espression has all of these meanings mentionned above, but, in order to really understand what you are requesting for, it would be better to give this expression within a more explicit context

Best regards
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3 hrs

I feel sick, I don't feel well

kibun is feeling
warui is bad
I feel bad is the literal translation

Kibun wa yoku nai also means I feel bad or I don't feel good.

VS
Kimochi warui! which is the Japanese equivalent of "Gross" in US English
Reference:

Six years in Japan

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7 hrs

I don't feel good/I don't feel well

Probably in first person singular.
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11 hrs

I don't feel well or I feel sick.

Kibun is the feeling or his/her mood.

Warui simply means bad or wrong.
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1 day 30 mins

irritable; discontent.

Since everyone else has gone with the physical illness definition...

This term can also be used when one is not in a "good mood" so to speak. When one is insulted, annoyed, or otherwise unhappy, their KIBUN (mood) is WARUI (bad).
Reference:

native speaker

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