First zombie ach
FIRST_ZOMBIE_ACH80.9%

Achievements and their recorded unlock rates.
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FIRST_ZOMBIE_ACHPUZZLE_ACHBOOM_ACHFIRST_TOY_ACHESCAPE_RC_ACHBASEMENT_BOSS_ACHESCAPE_HOUSE_ACHHOSPITAL_BOSS_ACHESCAPE_HOSPITAL_ACHISLAND_BOSS_ACHEASY_ACHMEDIUM_ACHSHOOTING_RANGE_ACHHARDCORE_ACHHORDE_MODE_ACHNGP_ACHSURVIVOR_ACHSURVIVOR_15_ACHTOYS_ACHULTRA_HARDCORE_ACH