In Marvel's Ultimate Universe, Magneto’s son Quicksilver, resulting in Magneto seeking retribution by initiating a plan that would kill millions, including many prominent Ultimate heroes.
The Ultimate universe is a separate parallel world where readers could follow modern and reimagined versions of their favorite characters unburdened by the continuity or storylines of the mainstream Marvel. Clint Barton was one of the founding of SHIELD whose work in Black Ops saw him elevated to public hip with the Ultimates, his world’s version of the Avengers. Unfortunately, Clint went through a rough patch after his family was murdered in Ultimates 2, becoming violent and hostile to his teammates, in and off of the field. In Ultimates 3, the Ultimates investigation into the sudden death of teammate Scarlet Witch was interrupted by her father Magneto who took her body to mourn with Quicksilver. While the Ultimates followed Magneto to his former base in the Savage Land, other learned Wanda was killed by one of Hank Pym’s Ultron robots, jealous of Scarlet Witch's close relationship with her brother.
In Ultimates 3 #5 by Jeph Loeb and Joe Madieura, the Ultimates plus X-Men’s Wolverine battle Ultron and his android duplicates. Despite appearances, the androids were no match for the real Ultimates as they were destroyed following father whose approval Quicksilver had been seeking his entire life.
This series, which was released to decent sales but also poor reviews, served as the prelude to Ultimatum. Having lost both of his children, the grieving Magneto blamed humanity and used Thor’s stolen hammer Mjolnir to help boost his powers so he could shift the planet’s magnetic poles. This triggered global catastrophes all over the world including a massive tidal wave that swept through Manhattan. This plus Multiple Man’s duplicates acting as suicide bombers killed millions of people ranging from civilians to of the Ultimates themselves. Throughout Ultimates 3, Hawkeye is portrayed as acting out of grief, willingly putting himself in danger so he could re his family in the afterlife. Much to his chagrin, he continues to survive despite facing opponents like Sabretooth, trapping him in a cycle of self-loathing and recklessness bordering on suicidal.
The problem with this is not only the event it created but also its lasting impact on the Ultimate Marvel world. Ultimatum was critically panned, considered by many to be one of the worst comic events Marvel has ever published. Ultimates 3 revealing that it was Doctor Doom who had manipulated Ultron into killing Wanda was one thing, but the revelation that Quicksilver had been alive throughout Ultimatum was another head-scratcher as it negated any logic that Magneto had in his genocidal actions. Although it redeems Hawkeye whose outlook and mentality would improve over time, this moment begins a dark period for the Ultimate Marvel universe that they never truly recovered from.
