This chapter uses six cases to describe how ethical and compliance failures arise and how ethical lapses harm clients, firms, and the markets. The chapter then distills actionable lessons for practice. The cases include JPMorgan Chase’s “London Whale” oversight collapse, UBS and the manipulation of the London Interbank Offered Rate, the 1Malaysia Development Berhad corruption and money-laundering scandal, Edward Jones and undisclosed revenue-sharing conflicts, Wells Fargo’s systemic sales misconduct, and Morgan Stanley’s client data protection failure. Weak governance and monitoring, hidden incentives and poor disclosure, toxic or collusive cultures, inadequate Anti-Money Laundering and Know Your Customer controls, complacent data security, and silenced voices unite these cases. The chapter also discussed the role of the Securities and Exchange Commission (SEC), the Commodity Futures Trading Commission (CFTC), the Office of the Comptroller of the Currency (OCC), the Financial Conduct Authority (FCA), and statutes and rules including the Dodd-Frank Act, the Volcker Rule, the Foreign Corrupt Practices Act, the Gramm-Leach-Bliley Act, and the transition from the London Interbank Offered Rate to the Secured Overnight Financing Rate in combating ethical breaches. Behavioral drivers of unethical behavior, including overconfidence, groupthink, motivated blindness, normalization of deviance, and diffusion of responsibility, are mapped to control failures and client harm. The chapter concludes with best practices that integrate regulatory requirements, cultural interventions, and behavioral strategies, including comprehensive surveillance and escalation, transparent conflict disclosure, incentive realignment, robust Anti-Money Laundering and Know Your Customer programs, privacy-by-design data governance, protected whistleblower channels, and continuous ethics education.