What is Valeant doing that is illegal/unethical? After reading the article and your comment I still don't really understand what they did. All I know for sure

What is Valeant doing that is illegal/unethical? After reading the article and your comment I still don't really understand what they did. All I know for sure is that Valeant buys a lot of pharmacies, and one of them accused them of fraud? What are the specifics of what they're doing, and how is it harmful to consumers?