Format a FileVault 2 encrypted disk

When you still have your password and have lots of time, you can cleanly disable FileVault2 from the Preferences pane. When you lack either one of these, another option is available: formatting your whole drive and losing your data.

When losing data is not a problem, you can use diskutil to force a wipe of the disk. Thanks to Alex Cabrera, whose solution I am simply mirroring here.

Use diskutil cs list to get a list of the available volume groups:

CoreStorage logical volume groups (1 found)
+-- Logical Volume Group FFF239C7-D4CB-4B93-B99E-0011AB4A17FF
    Name:         MacBookPro SSD
    Status:       Online
    Size:         499418034176 B (499.4 GB)
    Free Space:   0 B (0 B)
    +-< Physical Volume E5DDBA82-4F9B-463F-83AF-871C262ABDD8
    |   ----------------------------------------------------
    |   Index:    0
    |   Disk:     disk0s2
    |   Status:   Online
    |   Size:     499418034176 B (499.4 GB)
    +-> Logical Volume Family 934054A8-BEE0-45CC-98B5-71B9610C4909
        Encryption Type:         AES-XTS
        Encryption Status:       Unlocked
        Conversion Status:       Complete
        High Level Queries:      Fully Secure
        |                        Passphrase Required
        |                        Accepts New Users
        |                        Has Visible Users
        |                        Has Volume Key
        +-> Logical Volume 2B29927E-C421-481A-98F9-0ECB076F3C1E
            Disk:                  disk1
            Status:                Online
            Size (Total):          499071844352 B (499.1 GB)
            Revertible:            Yes (unlock and decryption required)
            LV Name:               MacBookPro SSD
            Volume Name:           MacBookPro SSD
            Content Hint:          Apple_HFS

Copy the UUID of the Logical Volume Group in this case it is FFF239C7-D4CB-4B93-B99E-0011AB4A17FF.

Then wipe the volume group:

diskutil cs delete FFF239C7-D4CB-4B93-B99E-0011AB4A17FF

After that you can use the regular graphical Disk Utility to create a new partition on your Mac.