Ginni Rometty

IBM’s $34 billion purchase of enterprise software company Red Hat is not only Big Blue’s biggest deal ever but one of the largest tech deals of all time. Rometty is pitching the acquisition as key to IBM’s “hybrid cloud strategy,” in which clients manage their infrastructure in both internal data centers and the cloud. The deal could define Rometty’s tenure, which has seen sales shrink 20% over five years to $79.6 billion.