The ethical implications of running a business are usually not dependent on the size of the business. A business of any size can and should try to have an ethically correct decision making process. Being ethically appropriate involves ensuring the welfare of all the stakeholders of the business. This includes suppliers of the business, the shareholders, the employees, the consumers, the other firms in the market, people in the vicinity of where the business is located that are affected by it presence, among many others.
A business can take many decisions that are completely legal and for which it would face no prosecution but being ethically correct demands a little more from the business. For example, a business that produces processed food may be located in an agricultural community that could supply all the raw materials required, the ethically correct decision would be for the business to source as much as possible locally even if it comes at an expense that could be avoided by importing from a local cost foreign producer. The business could make an effort to introduce technology and provide information to the local producers so that their operations can become more efficient which would reduce the costs of what is supplied. Another example could be of a business located in an area where the unemployment rate is very high but those that seek employment do not have the skill sets required by the business. The business could start some training programs to increase the skills of people in the area and when it is done hire them instead of seeking laborers from elsewhere.