Mortal Shell: Enhanced Edition

I followed the seeds from psnprofiles.com and was able to unlock this acheivement.
It says you have to beat every corrupted shell as the final boss once.
Here are seed numbers that will lead you to all 4 unique final encounters:
1. Harros, Eredrim & Solomon, Tiel = 185744
2. Harros, Eredrim & Tiel, Solomon = 832720
3. Solomon, Eredrim & Tiel, Harros = 767553
4. Solomon, Harros & Tiel, Eredrim = 720864

I would strongly recommend playing these 4 seeds when you start the DLC to unlock this achievement.

Note:
I played random seeds for my first 2 cycles. Even though I fought Eredrim and Solomon in these cycles, the achievement did not unlock for me till I played all the above seeds .
It took me 6 cycles.
1. 892978 played as Eredrim and fought Eredrim
2. 821796 played as Solomon and fought Solomon
3. 767533 played as Harros and fought Harros
4. 185744 played as Tiel and fought Tiel
5. 720864 played as Hadern and fought Eredrim
6. 832720 played Shell-less and fought Solomon

Hello its my first post on TA and sorry for my bad english.
You can add custom seeds in setting before start a new cycle. Apparently that modify variations of the dark shells at the end. One custom seed is the same for everyone doing this custom seed. Normally.
I searched informations and found these variations after doing 10 random cycle. Its not all variations but the 2 first custom seeds help me to get the achievement. Maybe these are more rarest. Hope this help you and maybe its the one missing.

411856 Solomon / eredrim + tiel / harros
173141 harros / eredrim + tiel / solomon
950362 solomon / eredrim + harros / tiel
106586 harros / eredrim + solomon / tiel

You can share others in the comments to help