How to reject an offer?

After all rounds cleared successfully during HR discussion for offer she told they can't offer more than my current. If that was the case why can't they inform initially before taking interview.

Once we accept multiple offers, how and when should be reject them before joining in a good way? And do companies blacklist if we reject the offer after accepting?

I have accepted job offer and then during notice period I got multiple job offers and accepted few of them, now one week before I want to reject other offers, I want to know will it effect my professional branding? And how to reject other offers gracefully without affecting professional relationships with recruiter and organisations ? Please help here

Right now I am working with IBM and got an offer with Deloitte.which organisation is better?

Sorry for being a pussy but I'm very new to this. So I accepted an offer from a company and did the BGC docs and all. 2 month later, now I have a better offer that I want to join. I'm sure I don't want to join the first company. Was gonna call the HR now, but what do I say??

I got an offer, I knew the role was not great but still went ahead to see if pay would be better (75% up). But I still would like to try for a better role and not accept this. I need your suggestion on how to do this, so that I won't be blacklisted for future opportunities of the offered company.

I recently received a counter offer from one of the big 4 company.. I had initially decided not to join. I am reconsidering my decision and would appreciate your advice on the potential consequences. Specifically, I am concerned about the risk of being blacklisted or facing negative if I choose not to join the company even after accepting their counter offer. Is there a possibility of affecting my future opportunities with the same company? Do they black list for rejecting their counter offer?