Most founders treat customer complaints like fires to put out—quick refund, apology, move on. But the fastest-growing D2C brands flip the script: they see complaints as raw, unfiltered data that fuel innovation, sharpen messaging, and build loyalty. Every angry email is a signal, not noise. Ignore it and you bleed retention. Embrace it and you turn frustration into a growth engine. This blog breaks down why complaints are your secret weapon for growth, with frameworks, tools, and real-world examples like Bombay Shaving Company.