In The Daily Show's April 14, 2022 video CP Time: The History of Black Classical Music comedian (among other titles) Roy Wood Jr. mentions George Bridgetower:
George Augustus Polgreen Bridgetower (11 October 1778 – 29 February 1860) was a British musician, of African descent. He was a virtuoso violinist who lived in England for much of his life. His playing impressed Beethoven, who made Bridgetower the original dedicatee of his Kreutzer Sonata after they presented its premiere performance.
Classic FM's July 22, 2020 Who was George Bridgetower? The violin virtuoso who fell out with Beethoven is an interesting read, and explains that Beethoven wrote his Violin Sonata No. 9 "for" him:
During an episode of Beethoven: The Man Revealed on Classic FM, Beethoven expert John Suchet said of the brilliant young violinist’s arrival in the musical capital: “With such credentials he was swiftly introduced into aristocratic circles in Vienna.
“And such was his skill on the violin, he was taken to meet Beethoven.”
Beethoven was deeply impressed by Bridgetower’s virtuosity and composed a sonata just for him – his Violin Sonata No. 9, of which Suchet says: “Violinists today regard it as the Mount Everest of violin sonatas. If you can play that, you can play anything.”
Bridgetower and Beethoven played the sonata together, on violin and piano. A glittering assembly gathered to watch the pair, and the performance was a triumph. Beethoven dedicated the sonata to the young violinist, calling it the ‘Sonata per un Mulattico Lunatico’.
Later the article says:
“And then, Bridgetower made a mistake. A mistake he would regret for the rest of his life,” Suchet says. “He made an off-colour remark about a lady that Beethoven knew. And Beethoven was furious.”
The composer withdrew his dedication, and the sonata would come to be known as the ‘Kreutzer’ Sonata instead, after the French violinist Rodolphe Kreutzer.
and finally:
The second tragedy, Suchet says, was that Kreutzer received the manuscript in Paris, took one look at it and declared it unplayable. Despite it bearing his name, he never once performed the sonata in public.
Question: Is the Violin Sonata No. 9 a particularly difficult Beethoven violin part to play? If so, what is it exactly that makes it so challenging?
For reference I've found this 1962 performance by David Oistrakh (violin) and Lev Oborin (piano) with the manuscript shown in the video portion. Several more performances are linked in The Listener's Club's May 24, 2019 Beethoven’s “Kreutzer” Sonata: Five Key Recordings "Here are five contrasting interpretations of the “Kreutzer” Sonata."