Final answer:
Benedict Arnold, after suffering a series of personal and professional slights throughout his military career during the American Revolutionary War, notably being overlooked after the Battle of Saratoga, eventually committed treason by planning to surrender West Point to the British.
Step-by-step explanation:
Benedict Arnold: America's Most Famous Traitor
The individual who planned to turn over West Point to the British is Benedict Arnold. Arnold's discontent began after the failed attempt to take Quebec, where his ambition and battle prowess did not yield the results he hoped for, nor did it garner support from French Canadians. Arnold's frustrations were further magnified after the Battle of Saratoga, where his contributions were overlooked, and he was passed over for promotions. Following his recovery from a leg wound and appointment as the military governor of Philadelphia, Arnold's personal conflicts and feelings of being continually slighted by the American side led him to marry a woman from a Loyalist family and eventually to cross the line into outright treason. The final act of his betrayal was his infamous plan to surrender the strategic American fort at West Point to the British, for which he is known as the most infamous traitor in American history.