This question may look like a duplicate of: How to uninstall postgresql on my Mac (running Snow Leopard) however, there are two major differences. I\'m running Lion and I\'m
Uninstallation :
sudo /Library/PostgreSQL/9.6/uninstall-postgresql.app/Contents/MacOS/installbuilder.sh
Removing the data file :
sudo rm -rf /Library/PostgreSQL
Removing the configs :
sudo rm /etc/postgres-reg.ini
And thats it.