X-Men's New Way of 'Pruning Timelines' Is More Brutal Than The MCU
Warning: contains spoilers for Immortal X-Men #1!
While Loki eliminated timelines left and right, the X-Men are giving the God of Mischief a run for his money with the release of Immortal X-Men #1. Marvel's Multiverse is made up of an infinite number of timelines, and thus an infinite number of them are destroyed, either succumbing to entropy or "pruned" by the Time Variance Authority. But Immortal X-Men #1 shows a new way timelines are eliminated, and it's incredibly brutal...or perhaps sinister.
In Loki, the titular character is abducted by TVA agents immediately after the events of 2012's The Avengers and brought back to their headquarters which resides in a domain outside of time. There, he learns he's not the 'true' Loki but a variant caused through the Avengers' time manipulation seen during Avengers: Endgame. As such, to protect the integrity of the so-called Sacred Timeline, both Loki and his entire branching timeline must be destroyed or 'pruned' by the agents of the TVA, leaving no evidence of his existence behind.
As supremely dark as that fate may be, it's nothing compared to the elimination of timelines seen in Immortal X-Men #1. In previous X-Men books, Moira MacTaggart was revealed to be a mutant with a unique ability: upon her death, she reverts to the moment of her birth, retaining all her memories from her previous life (explaining her genius intellect) - but the timeline in which she lived is destroyed. In a way, this allows her to learn from her own future - but while Moira uses this power to inform people like Charles Xavier and Magneto about the inevitability of the mutant-human conflict through time, villains like Mr. Sinister seek to use Moira's power for their own personal gain.
After a contentious vote among the Quiet Council in which Hope Summers is granted a seat but Selene is not, an angry Mr. Sinister retreats to his lair...which contains a dozen clone Moiras suspended in vats. Sinister's plan becomes clear: his future selves have been uploading their own memories into the Moira clones, and upon their deaths, his present self acquires said memories to use as ammunition for conflicts to come. Every time Mr. Sinister uses a Moira clone, an entire timeline is doomed to die...all for information.
Sinister is very much a Machiavellian-type villain and it's well within his character to enact this plan, but killing entire timelines is still horrific. He even kills himself using this method, albeit his future selves. Loki glossed over the eradication of entire planes of existence, but the Immortal X-Men series begins with multiple atrocities, and only the writers know if the story will escalate from there.