Michael Corbat settled into an armchair at Citigroup Inc.’s Park Avenue headquarters last January and shared his strategy to make the bank boring. The past 11 months have seen him expand in businesses that are far from it.

Corbat, CEO of the New York-based bank, extended his reach into commodities trading as other firms retrenched, kept a proprietary trading desk that takes a looser approach to new rules than some competitors and expanded the company’s derivatives business to make it the nation’s second-largest. At the same time, he has sold or plans to sell consumer units in 19 countries from Japan to Peru.