To fully appreciate the next Kang the Conqueror story it's necessary to step back into some of the earliest Marvel Comics, even before Kang emerged. Thor in his regular series in Journey Into Mystery (issue #102 to be exact) encountered a time traveler long before he battle Kang as part of the Avengers.
That traveler was Zaarko, dubbed by Thor "The Tomorrow Man". He hailed from the 23rd Century and like Kang was a man out of his time, an ambitious man with criminal tendencies who felt his own time too civilized and peaceful. So he traveled to the 20th Century to find weapons to help him become master of his own time. He steals a C-Bomb (Cobalt Bomb), one which Thor was actually helping to test. Thor pursues his new enemy into the future and works with the authorities there to bring him to heel. Zaarko suffers amnesia and so is left to the mercies of his own society to find a place for him in it.
Zaarko returns in Journey Into Mystery #102 when his memory comes back to him thanks to the machinations of Loki and he returns to the 20th Century armed this time with an altered mining robot of devastating power. Thor has had his powers reduced by Odin for his disobedience in regard to Jane Foster so is ill-equipped to confront the menace. So he gives his word to Zaarko to return with him to the future and help make The Tomorrow Man the master of his own time.
In the future Thor keeps his promise, his reduced powers still ample to humble the pacifistic 23rd Century culture. He and Zaarko seek control of a computer that controls the world and have to battle against its own protective weapons to gain access. Once that is accomplished and Zaarko is in control, Thor feels his oath is complete and he turns on the man from the future and helps to capture him once more. And that's the last anyone sees of The Tomorrow Man for a very long time.
In Marvel Team-Up #9 Spider-Man and Iron Man join forces when buildings begin to vanish. They themselves enter a portal to the future of the 23rd Century and find Zaarko there.
He informs them that a menace is wreaking havoc both there and in their own time and he appears to help them find the enemy's fortress. They fight to gain entrance but discover to their dismay that the enemy is Kang the Conqueror and he has himself already captured the Avengers. Meanwhile Zaakro reveals his true motives and attempts to get the drop on Kang when Iron Man and Spidey are seemingly defeated.
Spidey recovers in the next issue, and learns that Kang as sent several "time bombs" into the past. These bombs will transform the areas in which they appear back to a more primitive time, thus rendering the modern world of the 20th Century more susceptible to attack.
Spidey gets away, finds a time portal and heads home and finds the Human Torch alone in the Baxter Building and available to help him. The two head out across the globe to stop the time bombs and are successful and join forces to stop the final one. The threat ended, the Torch tells Spider-Man the radiation of the bombs reminded him of the energy used by the Inhumans in their Negative Zone.
So in MTU #11 Spider-Man heads to the mountains of the Himilayas to find the Great Refuge and the Inhumans. He is successful and enlists their assistance. Then he and the Royal Family head to the future and confront Kang's forces. As it turns out despite some clever time paradoxes, Spidey and his helpers are successful in freeing the Avengers and the combined might of those heroes help to defeat the plot of both Kang and Zaarko the Tomorrow Man. But it turns out that Kang was perhaps not really there at all, but literally an empty suit, a puppet of sorts. With that information the heroes return home.
This is the beginning I think of the notion that Kang can be everywhere and nowhere at the same time, that there might be versions of Kang himself dotted through the time streams. This is on top of the idea that Kang changes into other entities through his non-sequential lifetime, which is already complicated.
More to come.