The Mighty Thor #150, published by Marvel Comics in February 1968, features a story titled "Even in Death..." written by Stan Lee and illustrated by Jack Kirby.
In the main story:
Thor confronts a villainous team-up consisting of Loki, Karnilla the Enchantress, the Wrecker, and the Destroyer.
The Wrecker overpowers Thor and leaves him for dead.
Thor's spirit encounters Hela, the goddess of death, but rejects her claim on him.
Revived by his own will, Thor returns to his body to battle his enemies.
Sif and Balder Odinsson confront Karnilla and Loki, and Sif is tricked into entering the Destroyer armor.
The Destroyer, now controlled by Sif, overpowers the Wrecker but weakens Thor in the process.
The issue also includes a back-up story titled "Triton," an origin story for the Inhuman character Triton by Stan Lee and Joe Sinnott.
This summary avoids mentioning spoilers for the resolution of the cliffhanger ending.