'''First Season'''
* Dan's reaction to [[spoiler: Masquerade having Hydranoid blast Drago even after he's been defeated. Even worse when Drago is sent to the Doom Dimension.]]
* The death of [[spoiler: Masquerade]] counts, simply for him being so calm and excepting of his fate.
* All the kids having to say goodbye to their Bakugan partners.
* Drago [[spoiler: becoming one with the New Vestroia's core]].

'''Second Season'''
* [[spoiler: Skyress leaving Shun, for the last time. After Shun's been busting his ass to save her.]]
* Mira's cry for her father is heart-wrenching as the Alternative explodes [[spoiler: with her and Keith's father inside.]]

'''Third Season'''
* The deaths of [[spoiler: Anubias and Sellon]] were surprsingly tear inducing despite the fact that the pair showed almost zero redeeming qualities. While [[spoiler:Anubias]] was by far the more sympathetic of the pair, watching [[spoiler:Sellon]] plead to live ''just'' long enough to see the ''perfect world'' her master planned to create was a very KickTheDog moment for Mag Mel.

'''Fourth Season'''
* After not seeing many of these Bakugan for years, it was great to see Preyas, Elfin, Tigrerra and the like again. What was ''not'' so great was watching them all [[spoiler:being slaughtered]] while trying to defend New Vestroia. It was all pretty horrible, but the death's of [[spoiler:Elfin, Amazon, Preyas and Tigrerra were probably the biggest tearjerkers.]]