What makes Guts extraordinarily strong?

Even before supernatural elements, Guts is superhuman by the standards of the Berserk world. He learned to wield his enormous sword by fighting from childhood with adult weapons — building strength and technique simultaneously. His physical resilience is extreme: he takes damage that would kill most fighters and continues. His pain tolerance, built from genuine repeated trauma, is real rather than performed.

What is the Dragonslayer?

The Dragonslayer is a blade approximately two meters long and several inches thick — heavy enough that it cannot be swung through the air quickly by normal physics, but Guts wields it with one arm. It was originally forged as a joke (a theoretical king's weapon, too large to be practical). After killing hundreds of supernatural beings, it has absorbed enough of their essence to itself become effective against spirits and apostles. The sword is now supernaturally charged by the deaths it has caused.

What is the Berserker Armor?

The Berserker Armor is cursed armor that removes the body's natural pain and injury limiters — allowing Guts to fight without being stopped by damage that would immobilize anyone else. The cost: the armor forces the body to function past the point of sustainable damage, potentially causing permanent injury, and summons a "Beast of Darkness" — a psychological manifestation of Guts' rage — that threatens to consume his consciousness.

How does Guts fight in the Berserker Armor?

With overwhelming, nearly uncontrollable ferocity. The armor makes him effectively immune to pain and shock response during combat, allowing attacks that no normal person could execute while injured. But Casca's (or later Schierke's) presence is required to call him back from the Beast's control.

Where does Guts rank among manga/anime fighters?

Among the very top of realistic-scale fighters — characters who win through skill, endurance, and tactical intelligence rather than energy blasts. He's specifically powerful in the category of "human who has transcended normal limits through experience rather than supernatural origin."