That, and they grossly underpay their workers, including by undoing the American tradition of subsidizing wages with benefits like healthcare, vacation time, childcare, education, etc. - healthcare shouldn't be tied to one's work load, but if it's going to be taken away, they should be paid by law enough to avoid falling on the state or emergency rooms or death avoidably, needlessly because billionaires want as much profit as possible at the expense of their worker's welfare.

If a company and their owners are paying too little to their workers, if too many are on welfare, can't afford healthcare or the basic needs, the company and owners should be penalized so hard they are compelled to do what's right for the society they benefit and profit from though that labor and use of resources. If they fail, break up the company, sell it off, or close it down - just don't make the penalty a rounding error that becomes just the cost of doing business as usual.

Multiple ways, but that's one big one.

To loan against stock they use the stock as collateral. So tax the use of collateral as if it was an advance on capital gains tax. They would pay about the same as if they sold directly but with more annoying paperwork because they have to pass extra audits and shit.