I strongly disagree... It was deus ex machina trash with a twist. Using the original ending would have left the audience wanting closure and not getting it. Instead, they wrapped it up nice and tight and King got to murder another kid.

I can totally agree with that. I found her to be one of the most humanly believable villains in any story I've seen or read. She'd fit in to so many real world situations as that exact person. Absolutely the kind of nut job you'd see having a meltdown tantrum as someone recorded her on their phone.

For reference: handmaids tail was published in 1985, the mist was published in 1980. There are probably examples of that trope prior to the mist, but the handmaids tale isn’t one.

The Handmaid’s Tale (it’s kinda funny how both you and a commenter replying to you misspell the name in two different ways) is going for a “The Lady or the Tiger” ending. Do you believe that Nick is actually part of the Resistance, or is he part of the state secret police? The narrative tricked us a little with the “relationship” between Offred and the Commander - can we trust anyone at all?

The epilogue also gives the narrative some verisimilitude. It’s pretending to be a historical document - how would the world post-Gilead react to accounts of what happened to women during Gilead? How would you interact with the Diary of Anne Frank if you didn’t know that she was killed in the camps?

I fail to see how it’s similar to “The Mist” here.