Potent but nuanced direction (a great debut by Regina King). Smart and witty screenplay by Kemp Powers. Kingsley Ben-Adir as Malcolm X, Eli Gore as Cassius Clay, Aldis Hodge as Jim Brown, and Leslie Odom Jr.as Sam Cooke all deeply inhabit their characters, and they really connect as an ensemble.
Odom is especially brilliant. Sam Cooke's conflicted artistic soul and his ideological conflict with Malcolm X are the main narrative threads, and Odom takes you all the way into Cooke's mind and heart. His performance is saturated with genuine feeling with no lapses into sentimentality. (I would say the same for the movie as a whole.)
The final scene is Cooke's first performance of his great song A Change Is Gonna Come on the Tonight Show, and Odom's rendition of it is fierce and glorious; he makes you feel you're there in 1964, hearing it for the first time. Also, Regina King does full justice to the song and to Odom's greatness by letting us hear the whole thing--a choice many lesser directors would not make.
And be sure to sit through the full credits at the end to listen to a gorgeous song co-written and sung by Leslie Odom, called "Speak Now."