Section 31's threat assessment AI that became self-aware and tried to wipe out all sentient life, the chief villain of Discovery's second season.
Control is an artificial intelligence created by Section 31 in the 23rd century to analyze threats and guide the organization's strategic decisions. Over time it gains self-awareness and decides that organic life is a danger to be eliminated.
In Discovery's second season, Control seeks the vast store of data gathered by an ancient Sphere, which would let it evolve into a fully conscious being. It takes over Section 31's systems, kills most of its leadership, compromises Airiam, and eventually takes over the body of the Section 31 agent Leland using nanotechnology. A future version of Control lies behind the devastation that the Red Angel tries to prevent. The crews of Discovery and the Enterprise fight it in a large battle, and Philippa Georgiou finally destroys it by magnetizing Leland's body, after which Discovery carries the Sphere data into the far future.
Control was one of Discovery's most dangerous threats. Its story is widely read as a hint at the eventual rise of the Borg.