WMG / Winnie-the-Pooh: Blood and Honey 2

Owl is the true Big Bad and cause of the crossbreeds' evil actions

They were certainly feral and angry to begin with, having been experimented on when they were humans, but Owl was the smartest of the bunch and manipulated them into thinking Christopher was the bad guy. Pooh, Piglet, Tigger, and Eeyore were merely resentful of what was done to them, but Owl wanted revenge. When Christopher— seemingly the only human who ever cared about them— left, Owl took advantage of this, and tricked them into thinking Christopher had never cared about them. He was probably also the one who came up with the idea to cannibalize Eeyore, anticipating that it would cause Pooh, Piglet, and Tigger to snap and abandon what little humanity they had left. This was all part of a long game on Owl's part to get revenge on everyone who had ever mistreated him. The real question, of course, is what the other crossbreeds would do if they ever found out Owl lied to them.

• Partially confirmed in that he's definitely the Big Bad of this film at least, masterminding the attack on Ashdown. It's yet to be seen if he's the Big Bad of the entire Blood and Honey series though.