With one memo, Stephen Elop [1] drove Nokia's market cap from its peak of over $57b in March of 2010 to a trough of less than $7b in July of 2012 [2].

[1] https://communities-dominate.blogs.com/brands/2011/08/coinin... [2] https://www.macrotrends.net/stocks/charts/NOK/nokia/market-c...