Use full-disk encryption (presumably this is table stakes for anyone with this level of paranoia) using two factors - your passphrase decrypts a keyfile, then the keyfile is used to decrypt the partition.
If you destroy the keyfile, then even knowledge of the passphrase won't allow you to decrypt the data. This can be used to defeat a rubber-hose attack [0].
Standard security vs. convenience trade-off applies, of course - if you keep the keyfile on a USB key, then if the USB key fails you lose access to your data. If you keep a backup of the keyfile somewhere else, then access to that backup plus a rubber-hose attack to get your passphrase allows an attacker to decrypt your data.