Don't want to explain too much here. It's plain simple. Do it on your own risk! I take no responsibility about any harm that you could cause by eliminating physycally a database from your machine. If you ever need to remove physically the MySQL installation from your Mac OS X based machine, just use the following commands and instructions.
1. Stop MySQL server:
sudo /Library/StartupItems/MySQLCOM/MySQLCOM stop
2. Remove files and directories:
sudo rm /usr/local/mysql
sudo rm -rf /usr/local/mysql*
sudo rm -rf /Library/StartupItems/MySQLCOM
sudo rm -rf /Library/PreferencePanes/MySQL*
/etc/hostconfig and remove the line MYSQLCOM=-YES-
4. Remove following files and directories as well:
sudo rm -rf /Library/Receipts/mysql*
sudo rm -rf /Library/Receipts/MySQL*
sudo rm -rf /var/db/receipts/com.mysql.*
That's it. Thanks.