The simple way to do it is to send the btc to an address for which the private key is unknown, thereby making it impossible to spend. Watch them not do this.
I guess you could send to a random address, but there’s an infinitesimal chance that someone in the future generates a key with that address, right?
Sure someone could randomly guess it but not likely. You don't need to have or know a private key to generate a valid checksum bitcoin address that can be sent to.
- Generate private keys at a rate in which you will be able to produce it in a reasonable time
or
- Outright reverse engineer the private key from the public key or other metadata
Then Bitcoin is broken and that 1bn is worth next to nothing.
They could also short Bitcoin before intentionally crashing it.