The phrase "massive hammer" refers to a very large and powerful tool used for hitting or pounding. It indicates great strength and force. Full definition
In this case, mankind's been pushed to the brink of destruction by monstrous entities known as Aragami, and only the God Eaters have a chance of fighting back thanks to their God Arc Weapons — weapons taking the form of massive hammers, pointy spears, oversized swords, and so on. (gamecritics.com)
Even though it's a little too padded with filler missions featuring the same roaming enemies over and over, laying into Aragami with massive hammers and swords that could cut dumpsters in half generally makes for some good times. (gamecritics.com)
While massive hammers and swords still have weight to them, combat still has an imperativeness to it that the series has been lacking heretofore. (shacknews.com)