Botín had big shoes to fill, not to mention whisperings of nepotism to dispel, when she took over Banco Santander, the eurozone’s second-largest bank, after the sudden death of her father in 2014. The shoes fit fine: Since then, she has steered the bank to higher profits and capital ratios. And her takeover last year of Popular—a failing Spanish bank whose assets gave Santander a home-­market edge—for a price of just one euro may be her company’s best deal ever.