The Beethoven Funerailles is sad, It is something like one who was beloved, and died, and is mourned by those who loved her, who number many.
The expression of the imp's face in Fuseli's Nightmare is evil and treacherous. He's a little reminiscent of Cheney. Furthermore, he's not done with the girl. He has no pity or sympathy for the girl. His lust and evil overpower all else for the moment.
Quite Mephistophelean.
Beethoven wrote nothing that was evil and treacherous. I don't believe he knew how.