The very last level is honestly not worth unlocking in my opinion. It is just a short (and dirt easy) re-hash of an existing bossfight to unlock a new costume. No scenes and no story. You also shouldn't need to do the grindy achievements to get all the levels (you only need 40 of the 57 achievements).
For completionists sake though, I would just gathering the silver stones in each level as they are usually really easy to find and net you an achievement for each story level.
If you want to do the grindy parry achievement though, I recommend getting max in the parry skill and just standing in front of the final boss in the first epilogue level. Super easy to parry with attacks that net multiple parries each. Still a grind but much faster than waiting for hesitant goblins... I have no idea where you could even attack something 100x without it dying though so that achievement is a mystery to me.
