Antonio Salieri (1750-1825)
A contemporary of Mozart, he worked at the Viennese court and eventually became Kappelmeister. There were rumours that he poisoned Mozart, and he even falsely confessed to poisoning Mozart when he was in his old age and a bit delusional, but these rumours are not true. Tried to take his own life in 1823.
Due to the works of Alexander Pushkin's 'Mozart and Salieri', and Peter Shaffer's 'Amadeus', Salieri has been unfairly painted as a mediocre composer, though this is also not true.
Instead of creating his own opera, when Salieri became Kappelmeister, he revived Mozart's 'The Marriage of Figaro'.