The Marvel multiverse has been through a lot over the years, even being destroyed in the build-up to Secret Wars. Sometimes, even the most unlikely of figures can have major effects on entire timelines without realizing it. That's exactly what happened when Wolverine took charge in the Age of Ultron storyline, leading to a lot of unexpected and unintended deaths.
Wolverine's actions in Age of Ultron (by Brian Michael Bendis, Bryan Hitch, Brandon Peterson, and Joe Quesada) were brutal but did help ensure that Earth-616 could eventually be restored following Ultron's annihilation of most of the world. However, doing so had some truly terrifying unintended consequences, which led to multiple timelines suffering similar (if not even worse) fates. Wolverine's assassination of an Avenger did serious damage to the multiverse and highlights the true danger of messing with space and time on that level.
Wolverine's Murder of Ant-Man Caused Time Quakes
The Age of Ultron event focused on the robotic villain successfully carrying out a sudden massive attack all across the Earth, leading to the wide-scale eradication of most of humanity. In the aftermath, the few remaining heroes left rallied together to devise a plan to fight back. Many of them followed Captain America on an ultimately doomed mission into the future, where they were ruthlessly taken down by Ultron's forces. But Wolverine and Invisible Woman went a different route, with far more lethal consequences.
Using the brilliant Doctor Doom's technology, the pair returned to the early days of the Avengers, before Hank Pym had constructed the first version of Ultron. Aware of the cost that this invention would take on the world, Wolverine ignored Pym's pleas and murdered the hero. This irrevocably changed the timeline and ushered in a new reality where magic became a far more pronounced element in the universe. Although Logan's actions would ultimately be reversed thanks to some additional time-travel shenanigans, the effects of Logan's attack almost broke the multiverse.
Wolverine's Actions Doomed Multiple Multiversal Timelines
In the aftermath of Logan's actions, a series of "time quakes" were felt across various timelines in the Marvel multiverse. One of the few positive results of this was the revelation of Angela, eventually retconned to be Thor's long-lost sister. But for the most part, many timelines faced a whole new slew of threats caused by Wolverine's actions. The timeline that briefly replaced Earth-616 was one where an alliance between Doctor Doom and Morgan le Fay eventually overwhelmed and wiped out the heroes. The Ultimate Universe was confronted by the massive Earth-616 Galactus, which threatened their entire world. The time quakes also had a lethal effect on multiple realities, dooming many of the ones seen in What If...?: Age of Ultron.
On Earth-14622, the Wasp's sudden demise emboldened Pym to make an even more ruthless version of Ultron, who wiped out the Avengers during their early battles. On Earth-62412, Tony Stark's death led to a more chaotic and dangerous version of Armor Wars. Earth-23223 saw Thor die suddenly during a battle with the Midgard Serpent, leading to Ragnarok. Each of these timelines was doomed by Wolverine's actions. Wolverine's actions may have given Earth-616 another chance at life, but it more or less doomed entire other timelines to grim futures. Age of Ultron's time quakes highlights the inherent danger of committing acts on a multiversal scale, as they can have truly wild consequences.