Guilty Gear XX Slash

Fight against EX characters:
Hold L2 while selecting the "Arcade Mode" option.

Fight against Gold characters:
Hold L1 while selecting the "Arcade Mode" option. Note: You cannot choose a Gold or Shadow mode character.

Justice:
Complete survival mode level 440.
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Kliff:
Complete survival mode level 420.

Guilty Gear #Reload characters:
Successfully complete Arcade Mode with character that appeared in Guilty Gear #Reload to unlock that version of it.

EX characters:
Successfully complete Mission level 2.

Alternately, proceed through survival mode to unlock EX and SP characters. Note: After level 500 you will face Gold characters instead of the EX versions, in the order they appeared in EX forms. After unlocking the SP versions, highlight the unlocked character and press Start, Right.

Mission art:
Successfully complete Mission level 1 to unlock that character's art.

Order-Sol Mission Level 3:
Unlock both Kliff and Justice as playable characters.

SP costume colors:
Successfully complete Mission level 3 to unlock that character's SP costume colors.