I don’t know why I think of this 60s story now and then. The gist is that civilization of undersea monsters (I think) are poised to attack our world. One guy steps forward volunteering to disclose all our secrets and is universally condemned as a traitor. Actually, the guy is taken to their world where he convinces them that our world is unbeatable. The last panel has him standing there as a giant claw comes down to pinch his head. All this is from admittedly foggy memory, but I think that’s the gist of it. Sound familiar to anyone?
“Titan, The Amphibian From Atlantis” (from Tales of Suspense #28, April 1962).
Wow! How did you do that? It looks like my memory was closer than I thought!
It’s a Stan Lee / Jack Kirby giant monster story from Marvel’s (Pre-Fantastic Four) Atlas period. I’ve read them all.
Was I right about the head pinching?
It’s Titan’s two weird hands reaching toward the hero’s head while the monster says,
“Prepare for your doom, Earthling!”
BTW, you may have read it as a reprint in the 1970s in Uncanny Tales from the Grave
I love all those Marvel bronze age reprint comics. Fun stuff.
I must’ve read it in the original- I never bought any Marvel reprints. I gave my collection to a friend’s little brother. Wish I could get them back 
I have a subscription to Marvel Unlimited. That’s where I refreshed my memory of the story.