Dragon Ball Z: Lord Slug

Piccolo sacrifices his ears because he knows that Namekians have extremely sensitive hearing. Gohan's high-pitched whistle would incapacitate Slug just as it caused Piccolo pain earlier. By removing his own ears, Piccolo can endure the whistling without being weakened, allowing him to support Gohan while the sound damages the villain.

Earlier, Gohan's whistle causes Piccolo to wince in pain due to his Namekian hearing, establishing this weakness.

Lord Slug is an ancient alien who has lived for centuries and is nearing the end of his natural lifespan. By obtaining eternal youth through Shenron's wish, he ensures he can continue his conquests indefinitely without aging. This makes him far more dangerous than a typical mortal villain.

The brief mention of Slug as an ancient villain hints at his aging concern.

The meteor was not a natural phenomenon but a disguised spaceship carrying Lord Slug and his army. Goku and Krillin believed they destroyed it by blasting it in orbit, but the craft actually landed safely in a city, allowing the invasion to begin.

The Z Warriors sense a threat approaching from outer space before the meteor is detected.

The Spirit Bomb gathers energy from all living things on Earth, making it exponentially more powerful than any individual fighter's ki attack. Even as a Super Namekian, Slug cannot withstand the combined life force of an entire planet focused into a single blast.

The Earth crisis deepens as life begins to perish, building toward the collected energy that powers the final attack.

A Dragon Ball is sewn onto Gohan's hat as a convenient way to carry it. During the battle with Slug's army, the scuffle causes the Dragon Ball to fall off, becoming part of the seven balls that Slug's men gather to summon Shenron.

The film specifically notes the Dragon Ball on Gohan's hat and its loss during the scuffle.

Lord Slug is a member of the Namekian race who has achieved an extremely rare and powerful transformation beyond standard Namekian abilities. This grants him significantly enhanced ki, physical strength, and durability far beyond what regular Namekians like Piccolo possess, making him one of the most powerful villains the Z Warriors have faced.

Piccolo himself is a Namekian, establishing the baseline power level that Slug far exceeds.

Goku experiences a moment of rage when he sees Krillin defeated and overpowered by Slug. This emotional response hints at his Super Saiyan transformation ability, though he does not fully transform in this film. The rage amplifies his ki temporarily.

The rage moment occurs specifically after Krillin is defeated by Slug.

Medamatcha overpowers young Gohan and fires a ki blast at him. Piccolo jumps in front of the attack, taking the hit meant for Gohan. This injury incapacitates Piccolo for much of the battle but demonstrates his protective bond with Gohan.

Gohan is nearly killed by Medamatcha before Piccolo's arrival.

After being injured and weakened, Piccolo uses a technique to transfer his remaining life energy and ki directly to Goku. This boosts Goku's power significantly, enabling him to gather enough energy for the Spirit Bomb despite his earlier exhaustion from fighting Slug.

Piccolo is injured in the battle but survives with enough energy to make this sacrifice possible.

The combined effort of the Z Warriors weakens Slug through Gohan's whistling and the deaths of his top lieutenants. Piccolo transfers his remaining ki to Goku, who uses the energy to form a massive Spirit Bomb. The Spirit Bomb strikes Slug and destroys both him and his machinery, saving Earth.

The final battle sequence follows the ki transfer and Spirit Bomb preparation in quick succession.