YMMV: The Forerunner Saga
- Mis-blamed: The Forerunner Saga is often pointed to as the 343 Industries canon source that changed Forerunners from ancient advanced humans to a separate species. The Forerunners and humans being separate species was actually established in the terminals of Halo 3, by Bungie themselves.
- Another common complaint is that the series turns the Forerunners and Flood into hyper-advanced species with mindbogglingly-advanced technology. Ignoring the fact that the first thing we've seen in the series is the ten-thousand kilometer-wide artificial world with a weapon designed to destroy all life in the galaxy, and the Flood are so terrible that such a weapon is needed to defeat them....
- Moral Event Horizon: The Master Builder crosses it when he uses a Halo to punish the San 'Shyuum for rebelling. Even his closest allies thought he crossed it.