You could use end to end encryption which uses one of the more secure and complex encryption/decryption methods available, and only give the private key to that one individual, and using a device which you know does not contain any hardware or software backdoors for any government or business entity. Rotating encryption keys on a scheduled basis can also help verify that only the recipient has access to the correct keys.

I haven’t done any real project which uses encryption, so don’t call me an expert on different algorithms or methods of implementation. However I’d also stress that being excessively paranoid about people wishing to steal your information is not necessarily healthy. If the information you are communicating is important enough that people may try to use highly technical ways of breaking the encryption, it is always easier and more practical for them to make you give them access to that information yourself, through social engineering, rather than through hacking.