destroyed 4 WordPress sites
examples ;-(

one
Fatal error: Cannot redeclare wp_richedit_pre() (previously declared in /home/purposek/public_html/wp-includes/formatting.php:3096) in /home/purposek/public_html/wp-includes/deprecated.php on line 3608

two
Fatal error: Call to undefined function _deprecated_constructor() in /home/paddling/public_html/wp-includes/widgets.php on line 176