Completely Uninstall MYSQL from Centos and Start from Scratch

1. Uninstall mysql server and clients.

sudo yum list installed | grep mysql
and uninstall all mysql-related packages (with "yum remove")

2. Delete the databases folder.

sudo rm -rf /var/lib/mysql/

3. If you have the remi repo enabled, disable it.

sudo vi /etc/yum.repos.d/remi.repo (and set enabled = 0)

4. Re-install mysql and mysql-server.

sudo yum install mysql
sudo yum install mysql-server

5. Start mysql and run mysql_secure_installation.

sudo service mysqld start
sudo /usr/bin/mysql_secure_installation