From Dragon Quest Wiki

Gigacrash is the upgraded form of Gigasmash, being a two-handed equivalent to Gigaslash.


Dragon Quest XI: Echoes of an Elusive Age[edit]

Gigacrash requires the Luminary to invest 36 skill points into the Swordmastery section of his character builder during the game's second act. It targets one enemy group and will deal up 440~460 lightning damage for 32 MP.