What part of the US Constitution is the most dangerous to a business? Why?

The Commerce Clause has historically been used to justify federal involvement in businesses operating in individual states, which has amounted to restrictions on business activity. The part of the Commerce Clause that has caused the most concern pertains to the idea that the states are prohibited from passing laws that burden interstate commerce or discriminate, usually by favoring state citizens over non-citizens doing business within the state. Many people condemn the Commerce Clause for allowing the federal government to restrict the economic activity of local businesses and individual enterprises.
A classic example of the effect the Commerce Clause has on business is in the medical marijuana industry. Laws that have legalized medical marijuana in individual states conflict with the Controlled Substances Act, a federal law that makes possession of marijuana illegal. Thus, Congress has the authority to ban the cultivation and use of marijuana within the states, because these activities affect supply and demand in the national marijuana market.