How can I disable Pi-hole or unblock ads for a single device?

Assuming you configured your router to distribute Pi-hole as your network's DNS server, you simply need to manually set the DNS server on the devices you don't want to use Pi-hole for.

For example, if you set your router to force all of your network devices but one person doesn't want to use Pi-hole, you can manually set their DNS server to bypass Pi-hole while still allowing the rest of your network to use it for ad blocking.