Long before Thor carried his hammer Mjölnir, he carried an axe named Jarnbjorn. This wasn't just a regular axe he picked up outside a woodcutter's shed one day, it was made of Uru, the same metal Mjölnir and most Asgardians' weapon are crafted from.
In addition to being a powerful battle axe, Jarnbjorn has a few enchantments place upon it making it far superior to just about any handheld weapon in the Marvel Universe.
It is charmed so that it cannot be destroyed and also has the ability to cut through anything... and that means anything - including Celestial armor.
Thor blessed the axe with his own blood, which gave it the power to slice through the impenetrable armor and it worked. He took out the Celestial called Apocalypse but eventually lost the axe to Kang the Conqueror before it found its way back to the Asgardian armory centuries later. Whenever Thor has trouble picking up Mjölnir due to his waning worthiness, he returns to his faithful axe.
Jonathan is a graphic artist, illustrator, writer, and game designer. Jonathan retired from the U.S. Army in 2017 and enjoys researching and writing about history, science, theology, and many other subjects. He writes for ScreenRant, CBR, NerdBastards, Listverse, Ranker, WhatCulture, and many other sites online. You can check out his latest on Twitter: @TalkingBull or on his blog: jonathanhkantor.com