I unlocked everything the game has, too. It's the funniest part of MetroidVanias to me.
The best thing in terms of achievement was getting 1000% with Axe Armor. The Nest of Evil was a nightmare.
But Hard Mode LV 1 defeated me. I only managed to defeat a couple bosses and then I had to give up.
This time I hope I can do it.
But any strategy is welcome!

Also, Order of Eclessia Albus Mode is very, very hard. The last bosses are amongst the hardest things I ever played.
I didn't try OoE Hard Mode LV 1. Maybe I will give it a chance if I beat the PoR one (or if I give up again, I hope not).