[FranksTV]

This is a bit naive -- agreements don't require written documentation to be binding, and there are lots of indicators that an agreement existed (listing him on the website for example.)

The real problem is that this relationship (and it's unresolved status) would need to be disclosed to future investors.

The best solution is to come to a reasonable agreement with the person about exiting them with some compensation for their work that is reasonable.

Walking away entirely is definitely possible, but it exposes the company to future liability, so it's worth cleaning up properly.