It seems weird at first, but, in hindsight, his arrival was inevitable. Ever since Lil B cried in a pet shop and Drake started rapping his drunk-dials, rap’s retreated sharply inward, and it’s as viable for big-name MCs to vent from the primal corners of the soul as to stunt about dames and diamonds. While Biggie Smalls confronted depression poker-faced on “Suicidal Thoughts,” still tough at the end of his rope, Kendrick Lamar, the heir to that widescreen classic rap tradition, changes his voice on “u” to sound like he’s crying.