You don't need the government for that - you just let people do whatever they want. Any sort of anti-monopoly legislation is a subsidy in a sense, because it gives those protected some degree of economic power that they wouldn't otherwise have, enabling them to make better deals etc. And there's nothing wrong with that in principle, if you believe in common good - but then the question of scope arises.

And we're talking about all kinds of monopolies. The effect that Amazon has is not so much on its own employees (although there are some obvious issues there as well), but on employees of all the competitors that it puts out of business. All those people also benefit from the lower prices that Amazon offers - but that is more than offset by the loss of income. It's kinda like Walmart - it's more affordable, but at the cost of making a lot of people poorer such that they need that high affordability. For the owners, it's a win-win, of course, because it creates a lock-in. But I don't see why we should accept that as a society.