Giant Bosses are large Bosses in Hyrule Warriors that, much like Bosses in the The Legend of Zelda series, have a weakness that is usually an item. They all appear in certain Legend Mode Scenarios.
Fire Breathing: King Dodongo appears in "The Armies of Ruin", "Ganondorf's Return", and "The Dragon of the Caves". Its Ocarina of Time counterpart appears in "The Water Temple" and "The Other Hero". King Dodongo's attacks include rolling around in a ball, stomping its feet, roaring, and inhaling to release a powerful blast of fire. Its weakness is throwing Bombs into its mouth while it inhales. It usually drops King Dodongo's Claws as Silver Material when defeated, and rarely, King Dodongo's Crystal as Gold Material.
Arthropod Cyclops Monster: Gohma appears in "The Sorceress of the Woods", "Ganondorf's Return", "Darkness Falls", "A New Disturbance" and "Watchers of the Triforce". Gohma's attacks include a large swipe, rapidly spinning, charging, jumping into the air and crashing down, stopping to charge a powerful blast from its eye, and firing a laser beam from its eye vertically or horizontally. Gohma's weakness, its eye, can be shot with the Bow when it periodically turns from red to blue. This happens after it has fired a laser beam or while charging its blast. It usually drops Gohma's Acid as Silver Material when defeated, and rarely, Gohma's Lens as Gold Material.
Poisonous Tree: Manhandla appears in "The Sorceress of the Valley", "Ganondorf's Return", "Darkness Falls", and "Watchers of the Triforce". Manhandla's attacks include spitting seeds that target the Allied Base, rapidly spitting seeds at their enemies, lunging with its jaws, uprooting itself and rampaging around with its heads swinging, or spewing a pool of poison. Manhandla's weakness is a large crystal in its bulb, which can be exposed by hitting all four of its heads with the Boomerang while they are not metallic. Sometimes Manhandla will expose its crystal without all of its heads stunned, but this is very uncommon occurrence. It will usually drop Manhandla's Toxic Dust as Silver Material when defeated, and rarely, Manhandla's Sapling as Gold Material.
Twilit Dragon: Argorok appears in "The Shadow King", "Liberation of the Triforce", and "The Usurper King". Argorok's attacks include charging, kicking up whirlwinds with its wings, and breathing a stream of fire that also surrounds it. Argorok's weakness is the tip of its tail when it glows blue, which can be pulled with the Hookshot to bring Argorok down to the ground. It will usually drop Argorok's Embers as Silver Material when defeated, or rarely, Argorok's Stone as Gold Material.
The Imprisoned appears in "Sealed Ambition" and "The Demon Lord". It is one of the only Giant Bosses whose weakness it not an Item. Its weakness is its eight toes, which can be destroyed to knock The Imprisoned down. The Imprisoned's attacks are the same as they are in Skyward Sword. It will usually drop The Imprisoned's Scales as Silver Material when defeated, and rarely, The Imprisoned's Pillar as Gold Material.
Dark Beast: Ganon appears in "Liberation of the Triforce" and Ganon's Fury. He is the final boss of Legend Mode and combines all of the attacks and weaknesses of the previous Giant Bosses. His right claw will charge a fire blast like King Dodongo while weak to Bombs, his left claw will charge a laser beam like Gohma while weak to the Bow, his shoulder spikes will rapidly fire seeds like Manhandla and then become weak to the Boomerang, and his tail will glow blue like Argorok while weak to the Hookshot. Each successful blow will break the part that was hit, disabling the attack it uses. Once all four parts are broken, Ganon will begin to repeatedly charge toward the Warrior and cause the gem on his forehead to temporarily glow after each dash. The gem is weak to the Bow while it is glowing and will finally make Ganon vulnerable to attack once it is struck. He will usually drop Ganon's Mane as a Silver Material, and rarely, Ganon's Fang as a Gold Material.
In Ganon's Fury, a mode featured in the Boss DLC Pack exclusive to the Wii U version, Ganon will also appear as a playable character. He shares many attributes to the other playable Warriors, but handles differently due to his large size.
Helmaroc King appears in "A New Disturbance" and "The Search for Cia" in Hyrule Warriors Legends and Hyrule Warriors: Definitive Edition. Helmaroc King's attacks include ground pounding, stomping on the ground to create shockwaves, and pecking the ground with its beak. Its weakness is hitting its beak with the Hammer while it is temporarily stuck in the ground after pecking. It will usually drop Helmaroc Plume as a Silver Material, and rarely, Helmaroc King's Mask as a Gold Material.
Phantom Ganon appears in "Watchers of the Triforce" in Hyrule Warriors Legends and Hyrule Warriors: Definitive Edition and is one of the only Giant Bosses whose weakness is not an Item. Phantom Ganon's attacks include spin attacks, teleporting, duplicating himself, and shooting energy balls. Its weakness is its own energy balls, which can be hit back toward it like the fight in The Wind Waker. After its health has been reduced to about half, it summons a second sword and hacks away with both of its swords. With Phantom Ganon now using close range melee tactics, its weakness is its backside. It will usually drop Phantom Ganon's Cape as a Silver Material, and rarely, Phantom Ganon's Sword as a Gold Material.