Chose a career that helps mankind rahter than harms. Consider the Company you might for... do they have harmful practices, such as animal testing, create or distribute harmful products as tobacco, alcohol, weapons, or pronography. Avoid companies that practice unethical business practices or violate pollution laws.
In short, work for companies that are legal, non-violent, honest, and cause no harm to man, beast or the environment....
It will be a difficult task since many companies are diversified and house many companies. Even one's Government may violate ones principles. It may be a very difficult task to work for a completely harmless employer. Even if you work for your self, you may have dealings with others that you do not know all about.