Slavery is a strict outcome of unregulated capitalism. That's literally where "classical" slavery originated. Money gave slavers power, and they used that power to abduct people into slavery which made the slavers money.

Better veiled versions of that plopped up all through the centuries past slavery (and before that) as well. Factory towns were exactly that as well. You worked in the factory/mine and instead of money you received company vouchers as income. These vouchers you could only spend in the company shops and company housing. So if you tried to leave the company, you had nothing. And since they could essentially charge you whatever they wanted, they'd make sure you earned less than what you needed to survive, so that you'd rack up debts while working there. So if you left, you were forced to pay your debts, and if you couldn't (and you really couldn't in most cases), you'd just go to prison, and be forced to work in the mine/factory anyway.

Completely unregulated capitalist sectors (e.g. the mafia) use the same exact system to this day.

Have, for example, a look at human trafficing rings.