Carnage (Sony's Spider-Man Universe)

For me it's this.

Despite not having appeared yet cinematically, I feel that in the next Venom movie, Venom may elaborate on the symbiote/Klyntar species creation, where we may finally get to see Knull as he is a crucial factor in the creation of the Symbiote species. Plus, Knull currently serves as the unseen overarching antagonist of the Venom film series as he is responsible for the creation of all non-earthborn Symbiotes, making him responsible for the creation of Venom and Riot, and technically the "grandparent" to Carnage.