There are programs that overwrite your harddisk with random data, cluster by cluster. I've needed one long ago for Windows, I don't know what you use, but I'm sure a search will help you out. That should be pretty safe.

Another idea would be to make on the new laptop completely new wallets for the crypto you've used and transfer your coins to the new wallets. Of course, you'll also need to change the passwords and 2FA for all the accounts if you are this paranoid.  But I think that proper full overwrite should do.