wp_delete_signup_on_user_delete()
Function: Deletes am associated signup entry when a user is deleted from the database.
Source: wp-includes/ms-functions.php:1130
delete_user
Action Hook: Fires immediately before a user is deleted from the database.
Source: wp-admin/includes/user.php:336
deleted_user
Action Hook: Fires immediately after a user is deleted from the database.
Source: wp-admin/includes/user.php:410
wpmu_delete_user
Action Hook: Fires before a user is deleted from the network.
Source: wp-admin/includes/ms.php:230