Alex Rodriguez, 54, 2007
By 2007, Rodriguez had already topped 50 twice with the Rangers (52 in 2001, 57 in '02), led the league four times and pocketed two AL MVP awards. He had yet to become enmeshed in the performance-enhancing drug controversies that later tainted his career, but the ever-controversial slugger had hit "only" 35 in 2006, his lowest total since 1997. He bolted out of the gate in 2007, homering in his final plate appearance on Opening Day against the Devil Rays, and hitting a remarkable 12 in the season's first 15 games en route to a record-tying 14 for the month.
It took Rodriguez two months to double his total, but he entered the All-Star break with 30. In August he hit his 500th career home run and he started September with eight in eight games. Alas, a 13-game drought followed, but he added two in his final four games to finish with a league-high 54 en route to his third MVP award. After that season he oped out of his 10-year, $252 million contract to sign a 10-year, $275 million deal with the Yankees.