IBM-Red Hat ($34B, 2019)

IBM paid a $34 billion premium for Red Hat in 2019, the largest open-source acquisition ever, hoping to revitalize its cloud business. Five years later, IBM's cloud market share sits at 4%, ranking a distant fourth behind AWS (32%), Azure (23%), and Google Cloud (11%). This acquisition underperforms #8 Quaker Oats-Snapple's $1.4 billion loss in strategic impact, as IBM failed to gain any meaningful traction despite Red Hat's 90% enterprise adoption rate.