If the drive was formatted encrypted, throwing away the encryption key (the password you set when formatting) is good enough to securely erase the data. This is the “cryptographic erase”.
If you did not format it as encrypted, you could try adding that encryption now. Once the entire disk is encrypted, that will allow you to “securely erase” it by again throwing away the encryption key. To encrypt an APFS drive that was not formatted as encrypted, attach the drive to your Mac, in the Finder right-click its icon, and chose Encrypt. A while back I was attempting to confirm if that encrypted the entire drive or just the present contents, but I’m afraid that question is still open. The answer to that question determines if you should be worried about items that you once had on the drive that have been deleted (but not overwritten), from remaining unencrypted on the drive or not. Depends on your level of paranoia how much effort you want to put into this.
Finally, you can always use Disk Utility to perform a multi-pass secure erase by writing zeros or random data to the SSD. On SSDs this is commonly not recommended because SSDs have finite write cycles and because their wear leveling makes it difficult to perform this operation correctly. However, that said, since this is a drive that is likely destined for the garbage, you don’t have to worry about write cycles and instead this is likely more about peace of mind. In that case, all you need is time. A 3-pass (DOE standard) or 7-pass (DOD standard) secure erase of a 2TB drive will likely take all night. Best to just let it do its thing while you sleep. But again, don’t forget the drive’s wear leveling can (and likely will) interfere with what you’re trying to achieve here. So again, best is likely to encrypt and otherwise…
If this is very sensitive data and you can’t rely on throwing away encryption keys, you would probably want to physically destruct the SSD. Not just the disk, but the actual flash chips. There are shredders that will do that and there are companies that have equipment to do this for you. Of course, I suspect if you destroy the drive you won’t be able to get a refund so the question really becomes how paranoid do you want to be or rather, is securely getting rid of this sensitive data worth more or less than what you expect to receive from returning a defective drive.
Me personally, I usually just use the cryptographic erase and live happily ever after. :)