Nothing, nothing happens. You can't just lie about slashing, the term "proof" is being used in the computational sense. The submission you're describing requir

Nothing, nothing happens. You can't just lie about slashing, the term "proof" is being used in the computational sense. The submission you're describing requires a cryptographic proof of that validator submitting two or more existing invalid blocks that they signed. You can't just falsify that without their private keys, so what you're suggesting is not possible.