You have to infringe on the trademark. So the company has a trademark for the domain name. This is kinda way too little information to give you a comprehensive answer, and I'm not a lawyer. You should seek the advice of a trademark lawyer.
You can trademark "boots" for an equine business. So it's doubtful that it's true that there is only one good thing that it could be used for. You could buy the domain and run an equine business on the domain and provided you haven't infringed on their trademark, you'd be technically, safe from a UDRP land grab.
But in your starkest example. You already know the answer to your question. The company has a trademark on the left of the dot portion of their domain name, and you want to buy the non-hyphenated version and sell it on to somebody else. As I said. I'm not a Lawyer. But you have probably broken the Lanham Act, and the aggrieved party, can sue you under that, with a max fine of $100k per breach. IIRC. Or they could probably just take you court, with untold outcome.
You'd need some fancy footwork from some top trademark lawyer(s) to mitigate your losses.