Carbon Market - What's the Key Risk?

If i'm a corporation or a large institution, and i'm looking to use carbon market to help meet my net zero commitments, what's the key risk that i need to be aware of? The ideal position is something that is robust enough, but also cheap enough. And if you look at it from a corporate's perspective, given the voluntary nature of what they're doing, there's going to be what i call a trade off between the cost that commitment and the reputational concerns of being accused of greenwashing. So all corporates are going to aim for, i imagine, that middle ground. But the biggest danger for the voluntary market is actually the same risk that the countries have