If you actually have access to ftp then it is very easy to delete WordPress.
Step 1: Delete All WordPress files from the directory except (wp-config.php).
Step 2: Delete Database.
Create a php file and put this code with proper information. [You can get your database information into your wp-config.php file]
Delete Database:
<?php
defined("HOST")? null : define("HOST", "put db host name from config file");
defined("USER")? null : define("USER", "put db user name from config file");
defined("PASS")? null : define("PASS", "put db password from config file");
defined("DBNAME")? null : define("DBNAME", "put db name from config file");
$con = mysql_connect(HOST,USER,PASS);
if($con){
$link = mysql_select_db(DBNAME,$con) or die("no database").mysql_error();
if($link){
$sql = "drop database ".DBNAME;
if(mysql_query($sql)){
echo $sql;
}
}
}
else{
echo "Not successful";
}
?>
Now execute the new file & delete wp-config.php.
So your database will be deleted and your WordPress uninstall successfully.