Sigma/Mega Man X4

Sigma is the final boss from Mega Man X4. While the Maverick Hunters and the Repliforce were busy fighting each other, Sigma took control of the Final Weapon and planned to use it on Earth, forcing X or Zero and the General to stop fighting in order to stop the Final Weapon before it could be used.

First form
Sigma is revealed as the true mastermind behind the battles and fights against X or Zero himself. Sigma's appearance is hidden by a cloak and he is armed with a beam scythe, resembling a Grim Reaper. This form can only be damaged by X's Rising Fire or Zero's Ryuenjin.

Sigma is constantly appearing and disappearing, and attacks by swinging his large scythe or firing several projectiles that crawl the ground. The projectiles can be avoided by jumping over them. When he appears in the corner of the room, he will use a scythe attack that covers most of the room. It can be avoided by using Wall Kicks on the opposite wall. The best moment to attack Sigma is as soon as he appears.

Attacks:
 * Shot Attack (ショット攻撃) - Sigma releases projectiles.
 * Scythe Attack (鎌攻撃) - Swipes the area with his scythe.

Second form
After taking enough damage, Sigma's cloak is burned out, revealing his new body. Although this is the same body, Sigma recoves his health and changes his attack pattern.

Sigma starts by using Scythe Throw, making his scythe spin around him. Afterwards he uses Laser Attack, throwing the scythe on the player's current position. His following attack depends on where the scythe lands: Boomerang Attack if the scythe hits the floor, and Laser Eye if it hits a wall. He then repeats his pattern. A good strategy against him is to stay close to a wall to avoid his attacks and make the scythe hit the wall. When Sigma prepares to use his Laser Eye, dash jump to the wall behind him and attack him from the wall while he is using the attack.

Attacks:
 * Scythe Throw (鎌投げ) - Sigma throws his scythe and it spins around him.
 * Laser Attack (レーザー攻撃) - Sigma throws his scythe in the player's direction. After hitting a surface it will release laser beams across the surface.
 * Boomerang Attack (ブーメラン攻撃) - If Laser Attack hits the floor, Sigma releases four boomerangs from his shoulders.
 * Laser Eye (レーザーアイ) - If Laser Attack hits a wall, Sigma fires lasers from his eyes, covering most of the terrain.

Third form
In his final form, Sigma controls multiple bodies. He has two main bodies named Gunner Sigma (シグマガンナー) and Earth Sigma (アースシグマ) and mini bodies shaped like his head. He constantly changes between forms, following the pattern of attacking with the mini bodies, Gunner Sigma, mini bodies, and Earth Sigma.

Mini Bodies
Three metallic objects resembling Sigma's head, each with an element. The red head releases fireballs, the yellow head electricity, and the blue head has a freezing breath.

Attacks:
 * Flame Bullet (炎弾) - The red head fires four sets of fireballs.
 * Electromagnetic Bullet (電磁弾) - The yellow head releases six spheres from its forehead, with split into electric currents after hitting a surface.
 * Ice Fog (氷霧) - The blue head releases a cold fog from its mouth.

Earth Sigma
Earth Sigma is the body that appears on the bottom left of the room. It is a giant disfigured head of Sigma.

Attacks:
 * Spike Attack (トゲ攻撃) - When Earth Sigma appears, spikes appear on the right wall and Earth Sigma attempts to push the player to them.
 * Slime Body (スライムボディ) - Earth Sigma starts sucking debris, also pulling the player, and releases the debris.

Gunner Sigma
Gunner Sigma is an armed cyborg-like body that appears on the top right of the room.

Attacks:
 * Clear Laser (薙ぎ払いレーザー) - Gunner Sigma fires a laser beam that covers the whole floor.
 * Tracking Laser (追尾レーザー) - Gunner Sigma fires a laser beam on the player's direction.