Reset a WordPress user password via FTP

wp_set_password( string $password, int $user_id )

Update the user’s password with a new encrypted one.

With known user ID

wp_set_password('password', 1);

With known user login name (username)

$the_user = get_user_by('login', 'Adam');
wp_set_password('password', $the_user->ID);

Reset a WordPress user password via MySQL