I handed my bitcointalk account to my friend few years ago and he started doing paid shit posting. Now I asked him to provide me the account login and when I checked that its simple got down voted.
Is there anyway to fix my account reputation?
If it were just paid shit posting as you describe then I don't think it would be that big of an issue. It appears (at a quick glance so maybe I'm wrong) that your friend was promoting an outright scam knowingly. That's the sort of thing that just doesn't go away with a thread and a good story. I'd say if you handed away your account years ago, that's an equally bad offense and likely won't get you much sympathy around here. You're probably risking more negative feedback to be totally honest. All you can really do is roll with the punches and try to rebuild a reputation.
I handed my account in 2017 and by then I used to have good reputation here. Then he started paid posting of some crypto based scams and something similar to that. Although I have edited those posts but still the other users opinion will still be there.
You can check difference in posts by the end of 2017 and before that.