I respectfully disagree. The Thunderbolts have such a great twist, at least the first team did.
The Masters of Evil on the other hand always felt a little random. I mean, just look at ‘em — a radioactive Chinese Commie hanging out with a Nazi war criminal, two Asgardians and an embezzler, of his own family’s money at the encouragement of his brother, which never made sense. What the heck is that? I’ll take the Thunderbolts, please.
Okay, so now I’ll put my pick out there for critique.
I would have put the Killing Machine — Ransak the Reject — and Karkas in the Eternals.
The OP would be right to point out this doesn’t answer his question. Except, it kind of does. What did the Eternals movie lack? Almost all the connections to the source material. Actually, the same thing could be said of Gaiman’s and Gillen’s series. Do they really resemble the Eternals? No, they don’t. The Eternals in the 21st century are a bit of a snoozefest. You can say a lot of things about all Kirby’s work in the '70s, and even the '80s including the Eternals, but it sure as heck wasn’t boring.
I don’t know how Karkas and the Reject would have fit in there, but the Eternals biggest issue was it really lacked the Kirby vibe. Sticking a couple of the most action-packed characters that the Eternals have in there would have livened it up quite a bit, brought some of that Kirby Krackle with Ransak’s power-rod.
I have no idea how they could have made it work with the story they told. But just look at this. If there was one thing that Eternals movie could have used more of, it was THIS.