Cassius Marcellus Clay was the son of one of the wealthiest slave owners in America and grew up to be the single most influential and most dangerous abolitionist in American history. He had so many duels with slavers, and won so many of them, that he became statistically the most dangerous duelist to ever exist in North America.
When his cousin, Kentucky senator Henry Clay ran for president, Cassius wanted to come campaign for him down South. Henry vetoed this out of concerns that Cassius would come down south and duel so many slave owners to the death that it could be considered election interference.
The Fat Electrician has an excellent video on the life and times of Clay, I highly recommend it. And if you're wondering, yes, Muhammad Ali was named after this Cassius Clay.