The fastest way you can delete the related products is by using Mysql queries. Please check below an example as I performed this operation on a product from the Magento sample data db (you just have to replace the SKU and product ID with your own data):
- Get the relation type ID, in your case it's 'relation' for related products relation by using the query:
mysql> select * from catalog_product_link_type where code='relation';
+--------------+----------+
| link_type_id | code |
+--------------+----------+
| 1 | relation |
+--------------+----------+
1 row in set (0.00 sec)
- Find your product IDs based on the SKUs you know you have and need the deletion of the related products associated to them:
mysql> select entity_id from catalog_product_entity where sku in ('24-UG06');
+-----------+
| entity_id |
+-----------+
| 15 |
+-----------+
1 row in set (0.00 sec)
- Visualize the associated products:
mysql> select * from catalog_product_link where product_id in (15) and link_type_id=1;
+---------+------------+-------------------+--------------+
| link_id | product_id | linked_product_id | link_type_id |
+---------+------------+-------------------+--------------+
| 2281 | 15 | 16 | 1 |
| 2282 | 15 | 17 | 1 |
| 2283 | 15 | 32 | 1 |
| 2284 | 15 | 34 | 1 |
+---------+------------+-------------------+--------------+
4 rows in set (0.00 sec)
- Delete the related products:
mysql> delete from catalog_product_link where product_id in (15) and link_type_id=1;
Query OK, 4 rows affected (0.00 sec)
- Check the results, you should have no related products for your product:
mysql> select * from catalog_product_link where product_id in (15) and link_type_id=1;
Empty set (0.00 sec)
As you can notice, I used the 'IN' condition in my queries. I did so so that you can reuse the same queries and instead of one value, you can replace the SKU and ID between brakets with a list of SKUs and product IDs if you need to run this over multiple products.
Good Luck!