While overlooking his conquered land, Ultron was confronted by past versions of Captain America, Wolverine, Iron Man, and Marvel Boy. The group warned Ultron that Kang the Conqueror will time travel to later from that point to wage war on him with an army of heroes and villains recruited from across time. The war will always end with Ultron winning, resulting in Kang repeatedly time-travelling to attempt to achieve victory. This, however, results in massive damage to the space-time continuum, causing infinite loops. The damage threatens all of existence, including Ultron.
Ultron is at first doubtful of the authenticity of the group's claims, and attempts to attack them. Protected by the Kree technology of Noh-Varr, the group simply leaves, leaving Ultron the choice to allow himself to lose to Kang, thus preventing the space-time damage, or not.
The foretelling comes to fruition, and Kang arrives with his army to battle Ultron. This time, Ultron allows himself to be destroyed. Disappointed that he couldn't inherit Ultron's rule over the world in the aftermath of a large-scale battle, Kang teleports his army away and leaves the timeline.