Ben Bernanke, then Chairman of the Federal Reserve, told Congress in March 2007 that subprime was contained. He will rightfully be remembered in infamy for that, but that wasn't the most egregious example of being wrong. Even putting it in those terms risks understating the problem and why it stubbornly lingers. Being really wrong is claiming that IOER will establish a floor for money market rates, and then finding out it actually doesn't.
No, what policymakers did especially in the early crisis period was altogether worse; they demonstrated conclusively that though they shared this world with the rest of us, they inhabited and continue to inhabit a totally different planet.
Given the anniversary date and our human affinity for round numbers (ten years or a lost decade), there is a desire to revisit some of the worst of the list which happened just before August 9, 2007.
My favorite has always been Bill Dudley, as I recounted last at the ninth anniversary of nothing being done: