Ever since your post about Jenny Greenteeth/Guinevere I'm imagining in this version she becomes a Lamia-like figure, traumatized by the deaths of all her children (I started out thinking Amhar & Loholt but we could also include her kids from Mordred if we wanted to go very dark and include Pedicide) she kills other children to make others know her own pain
Oooh, that's very dark. Maybe a bit too dark (which is always a worry considering Guinevere's varying characterizations and ability to engage with audiences)
Then again, Amhar, Loholt and Mordred's sons are reportedly killed by people Guinevere ought to trust - Amhar by Arthur, Loholt by Kay and Mordred's sons by Constantine (Arthur's cousin) or by the Benoic faction.
I think the "retaliation" angle may work if Guinevere's (racial/tribal?) affliations and tensions are more clearly defined - like her Cewri/Giantess heritage from Welsh myth sets the precedent for her turning monstrous against the Britons for long standing prejudice (potentially going all the way back to Brutus and Gogmagog).
(EDIT: Oh, it just came to me: Lamia was given the power of Prophecy as compensation by Zeus. Guess what is Guinevere's magical ability in Rise of Gawain?)