Final answer:
Heathcliff is responsible for Hareton Earnshaw remaining wild and uneducated as a form of revenge against Hareton's father, Hindley.
Step-by-step explanation:
The character responsible for Hareton's wild and uneducated state is Heathcliff. In Emily Brontë's classic novel Wuthering Heights, Heathcliff harbors a grudge against Hareton's father, Hindley Earnshaw. Following Hindley's death, Heathcliff assumes guardianship over Hareton and, consumed by his desire for revenge, deliberately neglects Hareton's education and refinement to humiliate Hindley's legacy. Heathcliff ensures that Hareton grows up without the benefits of education, manners, or social standing. The other characters in the options provided, Mr. Lockwood, Edgar Linton, and Nelly Dean, are not directly responsible for Hareton's upbringing.