I have undergone a bad contract with a client recently.
The client ended the contract and requested me to refund all money ($125) when he left so bad feedback. So since I didn't have enough time to deal with the client, I accepted his request and refunded all money. In this case, his feedback will be on my work history?
If not, how long does it take to go away from my history?
re: "In this case, his feedback will be on my work history?"
The job will completely disappear from your work history. No mention of the job will appear. No feedback will appear.
(But private feedback will still affect your JSS.)
re: "how long does it take to go away from my history?"
It could take a day or two.
You might be able to force a page refresh earlier by making a small change to your profile overview text.