Given all the comments earlier, I can confirm the safest option is Darik’s Boot and Nuke Dban for short

Originally, you would put it on a CD (USB now), boot it, and auto nuke the entire computer. This however works only if you have a Hard Disk Drive.

Alternatively, you can also use the software called “Eraser” by Heidi. You can download it for free.

If you have a solid state drive, and you’re worried about all your data, it is best to remove the drive, and keep it for yourself. If not, you do the following:

Option 1:

• Encrypt the hard drive, delete the partition. Create a new partition that’s encrypted, but the partition has to be a different format. (First you have Ntfs, and then go to xfs or xfat)

Option 2:

• Use the Eraser software, and overwrite the entire hard drive. Encrypt the drive. And then format it.

Option 3: make sure the SSD’s mapping system is corrupted, or changed, so that if someone tries looking into it, they’ll only see a block of code, but not the entire file.

Or, hear me out. Apple has a super outdated system, that when you make phone calls, there’s a high chance you’ll be listening to other radio frequencies too, before it gets adjusted automatically once the call is through.