As head of Microsoft’s competition law group, Rima Alaily’s main job is to help close mergers at one of the world’s most acquisitive companies by shepherding them through sometimes sticky antitrust reviews. In early 2021, though, Alaily had a different goal: killing a deal.

The team Alaily leads aimed to torpedo Nvidia’s $40 billion bid for chipmaker Arm, a deal Microsoft believed would harm it and others in the tech industry by raising the licensing costs for Arm’s chip designs (Microsoft uses chips based on Arm designs for servers and other products). Working under the supervision of her boss, Microsoft president Brad Smith, and with Microsoft’s outside counsel at the time, Jonathan Kanter, Alaily's team crafted the arguments Microsoft put forward to urge the Federal Trade Commission to intervene and block the deal, according to someone with knowledge of the situation. Last December, the FTC filed a lawsuit against the acquisition—which other prominent tech companies also opposed—and in February, Nvidia abandoned its bid for Arm.

Now Alaily is helping fend off similar efforts to sink one of the largest acquisitions in tech industry history—Microsoft’s $69 billion takeover of videogame publisher Activision Blizzard, which faces investigations by British and European regulators and the FTC, as well as opposition from Microsoft rival Sony. At the same time, she has been involved in Microsoft’s efforts to influence DC policymakers crafting a slew of legislation that could rein in the company and its rivals. And she has encouraged those policymakers to more closely examine markets controlled by powerful competitors such as Apple.