Easy. You use government power on them. You "coincidentally" hit them with an IRS audit, one that's incredibly hostile and refuses to resolve itself. You hit their business with every inspection possible, held to the most stringent of standards. Even if, and perhaps especially if, they don't own it, and you find a way to sufficiently hint to the business why exactly they're having these troubles. You have a cop follow them and nail them with every petty infraction in the book. Any government program they may be on, you inspect their compliance to the n-th degree. Layer heavy bureaucratic red tape on at every opportunity. Find ways to make them need a lawyer. Find a petty excuse to claim you suspect them of drug trafficking and inspect everything they own, which basically allows you to take everything they own, and effectively destroy or hold on to everything for years.
And that's if you have a goal of staying plausibly legal. If the mask is off for some reason, there's even more you can do. And these are just examples; if one truly took a survey of what the government could do to you without even stretching the law, I think we could produce a very thick and scary book.
Unfortunately, I don't think the capabilities of the NSA are bounded by your imagination.