WPDB Prepared Delete

by

I think you have just confused syntax with INSERT 🙂 According to manual the DELETE syntax is:

DELETE [LOW_PRIORITY] [QUICK] [IGNORE] FROM tbl_name
    [PARTITION (partition_name,...)]
    [WHERE where_condition]
    [ORDER BY ...]
    [LIMIT row_count]

No VALUES.

Rather than forming this query manually you should consider using $wpdb->delete() helper.