WARNING: The following contains spoilers for Venom #1, on sale now from Marvel Comics.
With the ability to be anywhere at any point in history thanks to his advanced time-travel technology, Kang the Conqueror has had the opportunity to meet almost every hero in the Marvel universe, and he's learned to despise the majority of them. Although Kang has willingly worked with his enemies against greater threats, like Conan the Barbarian's archnemesis Kulan Gath, he still recognizes them as threats to his long-term goal of multiversal domination and will rarely pass on an opportunity to eliminate them.
That being said, Kang has also proven himself to be more civil than most other villains, and the time-traveling tyrant has shown begrudging respect for heroes who have managed to leave an impression on him, such as Captain America. In Venom #1 (by Al Ewing, Ram V, Byran Hitch, Andrew Currie, Alex Sinclair, and VC's Clayton Cowles), Kang reveals that he holds one hero in even higher regard, openly referring to Eddie Brock as a close friend. This revelation is surprising for many reasons, not the least of which being that Brock and Kang have barely interacted with one other.
Since becoming the king of all symbiotes in the aftermath of 2020's King in Black (by Donny Cates and Ryan Stegman), Eddie Brock's life has been drastically changed. Now filling in the role that the dark god Knull once occupied in the center of the Symbiotes' hive-mind, Eddie has sought to undo the damage caused by his predecessor's recent invasion of the galaxy. Although this crusade has done a lot of good for the galaxy, it's also alienated Eddie from his son Dylan, who is often left alone with Sleeper, one of Eddie's original symbiote's children, serving as his only company.
In Venom #1, Eddie and a group of Symbiotes (named after each member of the Beatles) are attempting to rescue the crew of a relief ship taken hostage by Skrull space pirates when an unknown entity seizes control of "Ringo" and forces it to slaughter the crew. When confronted by Eddie, the entity ominously warns him that his reign as the Symbiote King will be short-lived and advises him to make peace with Dylan. Having discovered previously that he could link with Symbiotes living in different times, Eddie attempts to connect to a Symbiote in the future hoping to get an idea of what's to come. During the attempt, Eddie is granted brief visions of the future, one of which features Kang on his throne, referring to himself as Eddie's oldest friend and warning him that he can't stop his newest enemy, the monstrous Symbiote known as Bedlam.
The fact that Kang appears to regard Eddie as a friend is unusual because Kang and Eddie have had almost no interaction with each other in the past. However, while experimenting with his burgeoning omnipresence in Free Comic Book Day: Spider-Man/Venom #1's "Like Father, Like Son" (by Ram V, Al Ewing, Bryan Hitch, Andrew Currie, Alex Sinclair, and VC's Clayton Cowles), Eddie saw a vision of himself and Kang locked in an intense duel, hinting that some sort of conflict will occur between them in the future and making Kang's assertion that he's Eddie's friend seem even stranger. Given his unusual relationship with the timeline, Kang often experiences events prior to anyone else, opening up the possibility that his friendship with Eddie has only played out from his perspective.
Eddie has expressed interest in using his new abilities to undo many of the tragic events that have shaped his life over the years, and his meddling with history could lead to him establishing his pending friendship with Kang. Regardless, the two appear to be on a collision course that will end with them becoming either the best of friends or the worst of enemies.