After Enron, Valeant Pharmaceuticals is one of the largest corruption scandals of Wall Street. If you want to know the details, you just have to connect Netflix. In episode 3 of the documentary seriesDirty Money, you'll find The Drug Short episode. You'll understand what happens when barbarians take unethical decisions, although they were legal. Meanwhile, the regulator was on vacation in the US.
Highly recommended.
PS. If you don't have Netflix and you are interested on how to proceed like a Valeant executive in the energy sector, then you have to watch "Enron: the smartest guys in the room".