When it comes to the ultimate offensive devices, sheer power is always required. The strongest anime arms and devices pack enough power to not only defeat enemies with ease, but potentially doom everything around them - including those wielding them.
Some devices, like the Bustermarm of Fairy Tail, are impossibly big and can cut through anything. Others, like the Punisher from Trigun, pack incredible power. Then there are the likes of Ea from the Fate series, which literally created - and can end - Earth itself. If you ever find yourself facing a device like these, you'd better hope your opponent doesn't know how to use it.
Though technically a sword, Ea boasts more powers than merely the ability to slice and dice. Ea cannot be replicated, as it's made of materials that are not of this world. Powerful enough to end the entire planet, Ea created the world by cleaving it away from the heavens.
Not only does it have these incredible primordial abilities, it holds knowledge of fundamental truths about the universe. Only one person, Gilgamesh, can truly wield this incredible sword.
The Silence Glaive is the only spear used by Sailor Saturn. Its abilities include conjuring force fields, creating blasts, and dooming entire planets. The glaive also causes worldwide earthquakes, massive gusts of wind, and ultimate demise.
When Pharaoh 90 tries to absorb Earth, Sailor Saturn silently swings the glaive down to the ground, obliterating Pharaoh and Earth.
Few devices match the formidable powers of the Murasame. The blade carries a toxic curse that stops a person's heart seconds after entering the body. With no antidote for it, the only way to survive an offensive strike requires amputating the afflicted body part before the curse reaches the heart.
Murasame also possesses a trump card called Little War Horn, which activates when the user cuts themselves with the Murasame and successfully resists the toxin. This offers a short burst of power, but in exchange, the user experiences permanent chronic pain that remains even after the Murasame breaks.
If you declare everlasting hatred for your brother over a sword, it had better be a pretty incredible sword. The Tessaiga, also known as the Iron-Crushing Fang, was forged using Sesshomaru and Inuyasha's father's own fangs as material. This sword, capable of slaying 100 yōkai (demons) with one strike, appears to have a mind of its own, telling its wielder when to strike a target.
This incredible device is actually only half of a sword - its mate is the Tenseiga, which can conversely bring back 100 lives - arguably, an equally powerful ability. Inuyasha and Sesshōmaru's father divided up the blade and gave one to each son, hoping to teach them a specific lesson by its use.