I like the idea that the title might refer to Henry as well as to GOAT. We’ve seen the writers often like to show the same theme applied to different characters in an episode (e.g. the romance of David and Mary Margaret, Shawn and Ashley, and Rumple and Belle in “Skin Deep”; the theme “I don’t want to be you” voiced by both Henry and Regina in “We Are Both”, etc…)
As so many have observed, Henry has a strong record as “The Truest Believer” among the Good Guys and both Greg and Tamara have repeatedly referred to their belief in their cause. What if it comes down to a conflict between Henry and his captors in some way in which the most devoted believer wins?
I think Greg is less committed to their cause than Tamara. His primary goal was always to find his father, and secondarily to exact revenge on Regina and destroy magic. Since it appears his father is dead, he may have less motivation to sacrifice Henry, especially if he begins to see echoes of his younger self in Henry. I wouldn’t be too surprised to see him switch sides and help the CharmMillsStiltskins rescue Henry.
Of course, we haven’t yet seen Tamara’s backstory, but she seems more committed than Greg, so I would say she is “The Truest Believer” among the villains. What if the Good Guys somehow manage to capture her while they are searching for Henry? I can see Snow and Emma trying to question a defiant Tamara when an impatient Regina says “Enough of this!” and just rips out Tamara’s heart to force her to assist in the rescue, just as Cora used Aurora.