Original sentence: He is best known for his work for Hammer Film Productions, for whom he scripted many of their most successful and still-famous horror films, including The Curse of Frankenstein (1957) and Dracula (1958) (US: Horror of Dracula)
Edited sentence: He is best known for his work for Hammer Film Productions, for whom he scripted many of their greatest horror films, including The Curse of Frankenstein (1957) and Dracula (1958) (US: Horror of Dracula)