Harry Potter: The Worst Thing Every Order Of The Phoenix Member Did

Minerva McGonagall is, likely, the most steady-handed adult in the Harry Potter series. Stern, but empathetic; tough, but fair, Minerva holds her pupils, as head of Gryffindor house, to an exceedingly high standard, similar to the one in which she holds herself. To find a detriment to the Transfiguration teacher, one must look all the way back to her very early life.

Minerva's upbringing wasn't always an easy one. Her mother was a witch, and had never told her father, a minister. However, when their child began to display magical aptitude, she was forced to confess, forever fracturing the trust between the couple.

Things would improve for Minerva throughout her seven years in Hogwarts, finding identity, purpose, and excelling in virtually every aspect, from academics, to Quidditch. Her future was bright, being offered a position with the Ministry of Magical Law Enforcement right out of school.

Things changed when she met and fell in love with Muggle Dougal McGregor. Having accepted his proposal for marriage, Minerva then thought of her parents, the problems that it would cause, and the realization that being with McGregor would expel her from the wizarding community.

The very next day, McGonagall broke off the engagement with Dougal, offering him no explanation and leaving him for good, breaking the young man's heart. Minerva was unfortunately brutal and callous, but doing so meant that she would get to live life on her terms, rather than living an unhappily as a muggle.