McClellan was his own worst enemy

Explanation: George McClellan was an early commander of the Union’s forces during the US Civil War. Before the war, he was well-regarded, as he excelled academically and had graduated at the top of his class at West Point. “The Young Napoleon”, some called him.

When given command of the Union’s forces against the pro-slavery rebel Confederacy, however, he proved unequal to the task. He had a nasty tendency to overplan and underdeliver, and consistently, grotesquely overestimated the capabilities and numbers of the rebels he faced, snatching defeat from the jaws of victory on several occasions, and blaming his civilian superiors all the while.

Lincoln dismissed him after a time, and cycled through several equally disappointing commanders before stumbling onto General Meade, who made an honest effort at whipping the slaving secesh scum. Meade would gracefully step aside in favor of General Grant after Grant’s successes in the Western theatre of the war, and Grant would successfully prosecute the war to its end.