What is the best way to validate every single file on an external drive?

My mac is having a kernel panic every time I try to time machine this external drive.

I've tried disk utility but I'm pretty sure it doesn't actually check for much, except maybe for some directory structure. The scan is maybe only a few minutes long and it reports everything has fine.

Is there a command or app that will actually read every single file in the disk and report any corruption or IO error?

According to Apple, if you run First Aid on a volume, Disk Utility verifies all the contents of that volume only. This is from this site. First thing I'd do if run first aid on your drive. It takes about 30 minutes to verify my drive.