Well, defining Guts solely as a 'dragon slayer' kind of misses the forest for the trees in 'Berserk'. Sure, he ends up wielding the Dragonslayer blade, but the role he plays is this brutal, walking embodiment of human defiance in a world where gods and demons have all the power. He's not a chosen one; he's the guy who carves his own path with a slab of iron, literally and figuratively. The dragons he slays are more often metaphors—the monstrous systems of fate, the apostles, his own trauma. That blade becomes a symbol of humanity's raw, ugly, desperate will to fight back against insurmountable cosmic horror.
You don't read 'Berserk' to see Guts triumphantly save kingdoms from dragons. You read it to see if a man who's lost everything can keep swinging, can protect the tiny, fragile new family he's found, even as the universe itself seems designed to crush him. The 'slayer' part is almost secondary to the 'survivor' part. In a genre saturated with power-fantasy protagonists, Guts reminds you that sometimes the greatest strength isn't in winning, but in refusing to break. That last panel of him just... standing there, battered but not gone, says more than any epic kill scene ever could.