To take stock of the past year, Artforum asked an international group of artists to select a single exhibition or event that most memorably caught their attention in 2021.DARREN BADER “The Medici: Portraits and Politics 1512–1570” (Metropolitan Museum of Art, New York) My first trip to the Met in at least seventeen months provided placid, people-free galleries, tears of simple happiness, and blessedly bad network service. My special exhibition mission was not to merely relish Florentine masters on loan, but to attend an unofficial Bronzino survey (the routine-dulled Frick portrait [Lodovico