Primal 2h sword

The Primal 2 handed sword is the most powerful weapon in the game. However, it can only be used during dungeoneering. It requires 99 Attack to wield and 99 Smithing to make.

Trivia
The Primal 2h actually requires 99 Mining, Smithing, and Attack. This is because Primal ores are not sold by the Smuggler.

The Primal maul may be stronger than this weapon, but this weapon seems more efficient due to its accuracy. This is not a big factor, however, as both weapons require 99 Attack to wield.