After you press start, before you select new game, input the following.
|L1 x 3, R2 x 1
||Enable Dark version of the Revived Hunter.
|Left x 3, Right x 1
||Enable Ultimate Armour for X
||How to Unlock
||Defeat High Max in portals then find another portal to face Dynamo.Note, Can be rematched after defeating him.
|Fight High Max before Gate's Lab.
||First defeat Nightmare Zero then find another portal.
|Fight Nightmare Zero
||Go through a portal in any Nightmare Stage for the 1st time.
|Get to Gate's lab earlier
||Defeat High Max in Nightmare Levels.
|Play as Revived Hunter a.k.a. Zero.
||Defeat Nightmare Zero.