what is probably the greatest check or limit that congress has against the power of the president/executive branch?

The system of checks and balances in government was developed to ensure that no one branch of government would become too powerful. The framers of the U.S. Constitution built a system that divides power between the three branches of the U.S. government—legislative, executive and judicial—and includes various limits and controls on the powers of each branch.

i think it can have both positive and negative effects on businesses.

for example:

lets say you own a small business and taxes go up 4% that means it is going to cost your business more money to buy product to sell. but at the same time you make more money from the tax rise.

that is my theory.