you can completely remove MySQL and phpMyAdmin by using the following commands

#apt-get remove --purge mysql* 
#apt-get remove --purge mysql-server mysql-client mysql-common -y
#apt-get autoremove -y
#apt-get remove dbconfig-mysql
#rm -rf /etc/mysql /var/lib/mysql
#find / -iname 'mysql*' -exec rm -rf {} \;

Next to remove PhpMyAdmin use the following command

#apt-get purge phpmyadmin

You can also Autoremove and clean all dependencies using the Following command

#apt-get autoremove
#sudo apt-get autoclean