This is not original reporting, more of a summary of the other in depth and brutal coverage from the FT, NYT, BB, and WSJ over the last two and half years. Not a particularly clear summary either. I would recommend those if you are interested, and have linked some below.
https://www.ft.com/content/7c6700bc-2976-11e6-8b18-91555f2f4...
https://www.nytimes.com/2019/02/19/business/mckinsey-hedge-f...
https://www.bloomberg.com/news/articles/2018-07-08/mckinsey-...
https://www.nytimes.com/2019/02/19/reader-center/mckinsey-he...
https://www.nytimes.com/2018/06/26/world/africa/mckinsey-sou...
https://www.bloomberg.com/news/articles/2018-10-21/mckinsey-...
https://www.nytimes.com/2019/01/09/business/mckinsey-bankrup...
edit: A couple of people pinged me on the FT article, which was groundbreaking, and a one-week copy can now be found here:
https://pastebin.com/jqkAytZp