First you need to edit the file in: /etc/hostconfig and remove the line Since this is a system file I advise you to open it with nano in terminal: 

Open Terminal
sudo nano /etc/hostconfig
Enter your password if you're not authed yet.
Delete the following line: “MYSQLCOM=-YES-”
CTRL+X (This is the command for closing NANO, Enter the “Y” key to save the file and exit nano).

Second step: Make sure MySQL is not running. Open Terminal and copy and paste and run the following commands: 

sudo rm /usr/local/mysql
sudo rm -rf /usr/local/mysql*
sudo rm -rf /Library/StartupItems/MySQLCOM
sudo rm -rf /Library/PreferencePanes/My*
sudo rm -rf /Library/Receipts/mysql*
sudo rm -rf /Library/Receipts/MySQL*
sudo rm /etc/my.cnf

MySQL is now removed from your MAC.