In order to reset the admin password from phpmyadmin in Magento 2, please follow below simple steps.

1) Go to phpMyAdmin
2) Open table admin_user
3) Run the following sql query

UPDATE admin_user SET password = CONCAT(SHA2('xxxxxxxxNewPassword', 256), ':xxxxxxxx:1') WHERE username = 'admin';

Here, NewPassword -> Replace it with your password.

Thats it.