When Thor was calling for his hammer and ready to strike the back of the Accursed One, it deflected the hammer with a back fist. From reading stack posts regarding hammer, it should have not happen. "Thor's Hammer enchantment cannot be lifted, moved by anyone except Thor or Someone worthy".
Mjolnir's "cannot be lifted" property (which does not include "cannot be moved") only applies when it is dropped or set aside. (Thor volume 1) Adamantium has also proven to be impervious to a strike from Mjolnir, proving that it can be blocked, as well as trading blows with other weapons made from uru, the metal from which Mjolnir is crafted.
Mjolnir has also been damaged on several occasions, from being sliced in twain to being completely vaporized (by interrupting the bonds between its atoms).
Finally, enchantments on Mjolnir have been removed in the past. Specifically, it used to be able to be used for time travel, but that enchantment was removed by Immortus (with Thor's permission).
For the specific encounter you're referring to, I'll note again that Mjolnir's property "cannot be lifted" does not prevent it from being moved or deflected, and is only active when set down (or dropped), not swung or thrown.