My bf has a wart on his hand. He's tried OTC freeze off, liquid wart remover, also saw a dr. Who tried to freeze it & its still there. Whats left to try?

Freeze. Freezing with nitrous oxide or liquid nitrogen will destroy most, but may require several treatments. The wart has layers like an onion, and some are below the skin surface.If you only destroy the top part, it regrows from below.I routinely freeze them, cut the dead skin off and freeze again and recheck them in a week for final touch up as needed.
Warts. Each night before going to bed soak a cotton ball in apple cider vinegar, apply it to the wart and then hold it in place with a band-aid. Leave it on all night, or if you like, 24 hours a day but change the soaked cotton and band-aid each evening for a week. The wart will swell and may throb as it reacts with the vinegar and then start to turn black within the first two days and in two weeks gone.