It's a toss-up!  Either this:
Swamp Thing #34 "Rite of Spring" by Alan Moore, Stephen Bissette and John Totleben

Swamp Thing Vol 2 34.jpg
 Or this:
"The Sleeper Shall Awake!" by Jack Kirby, Stan Lee and George Tuska in Tales of Suspense #72 (this three-part story continues in Tales of Suspense #73 and #74)


Tales of Suspense Vol 1 72.jpg