Here is the full list of all 28 Original Journey achievements.
Finish mission Arrival On Shadow.
Finish mission A Clockwork Companion.
Finish mission The Ronin.
Finish mission Lord of the Forest.
Finish mission Battle Amongst the Trees.
Finish mission Missing Squad.
Finish mission The Old One.
Finish mission Jail Break.
Finish mission Final Guardian.
Finish mission Unsealed Ruin.
Finish mission True Dark.
Unlock all the level 1 weapons.
Unlock all the level 2 weapons.
Unlock all the level 3 weapons.
Unlock all the level 1 suits.
Unlock all the level 2 suits.
Unlock all the level 3 suits.
Fall off 20 times.
Finish level 20 of Giant Forest.
Finish level 20 of Psychedelic Swamp.
Finish level 20 of Shadow Core.
Finish level 20 of God's Dominion.
Earn 15000 Crystals in total.
Die 15 times.
Defeat Demonic Tree.
Defeat The Guardians.
Defeat Ancient Tortoise.
Defeat Origin Stone.