The villain diesel engine in the 2000 film Thomas and the Magic Railroad is Diesel 10.
Diesel 10 is a large, menacing diesel locomotive equipped with a hydraulic claw that he calls “Pinchy.” In the film’s plot, he hates steam engines and plans to destroy Lady, the “magic engine” whose railway connects the Island of Sodor with Shining Time. His scheme makes him the principal antagonist of the finished movie.
Diesel 10 is supported by two bumbling diesel shunters, Splatter and Dodge. They are sometimes collectively called “Splodge,” which can cause confusion when viewers remember the henchmen rather than their leader. The film’s villain is not simply named Diesel: that is a separate diesel character in the wider Thomas franchise.
The character later returned in Thomas & Friends productions, including Calling All Engines!, The Great Discovery and Day of the Diesels. Diesel 10 is based on a British Rail Class 42 “Warship” diesel-hydraulic locomotive, though his oversized claw and exaggerated personality are fictional additions created for the Thomas universe.