Ali's intensity came through in countless ways. It showed itself in his performances, in his interviews and in his adherence to his beliefs.
He rose to prominence in a time where it was dangerous for an African-American to be loud and intimidating. In interviews, Ali was just that.
When asked to go to Vietnam, Ali refused to participate in something he did not believe in and chose to go to jail instead.
He then had the intensity to will himself back to the title even when he was overmatched. Ali could take a punch as well as he could give them.
He fought ten rounds against Ken Norton with a broken jaw. He later went on to beat George Foreman after he successfully employed a strategy that involved Foreman wearing himself out by throwing punches while Ali covered and leaned against the ropes.
Ali's intensity may have been on greatest display when he fought Ernie Terrel. Terrel refused to call Ali by his new Muslim name. Ali told anyone who would listen that he was going to humiliate Terrel, and that is exactly what he did.
Between each big shot, Ali taunted Terrel with the question, "What's my name?"