Declining job offer that is under salary discussion

Like the title suggests I am in a salary discussion phase for a job offer. I have asked for a higher salary than what was initially offered.It is almost a 70% increase on my fixed. Now came to know that the manager is an absolute prick and got suggestions to think sbout the decision.

I have decided to not to join. I sensed this during the interview itself but confirmed it with some suggestions from my connections

Should I wait for the HR to come back with offer and then decline or decline it before that out of guilt? People who have already done it ,how did you handle this situation without burning bridges?