Kraid

Kraid is a green reptilian-like monster from the Metroid series. Kraid is one of the largest enemies Samus ever encounters as he takes up multiple screens at a time. Kraid first made its appearance in the original NES/Famicom Disk System Metroid as a part of the game's miniboss duo, the other being Ridley. Kraid, though not with an official rank, is a high ranking Pirate as he is a common boss in the series. Kraid shoots projectiles such as dagger-like spiked projectiles from his belly and navel as well as spinning boomerang-like nails from its fingertips as its main weapons. Kraid weighs over 110 tons (100 metric tons, or 220,460 pounds) and is more than 65 feet (20 meters) tall.

Metroid
In Metroid, Kraid is the boss of Brinstar. Due to lack of colors and the sprite's limited sizes, the artist's interpretation of Kraid for the game's artwork differed considerably from what the game designers had in mind. Kraid's artwork seems to show that in addition to its smaller size in this game (than all later appearances), it also appears to have a mullet of green hair that runs down its back and only two eyes. However, this is not the case as the “mullet” is actually the darker shade of scales while his third eye can be seen in the middle of its forehead as what appears to be a 'horn'.

There is also a fake Kraid Samus may encounter before fighting the real Kraid. However, since Kraid's Hideout has multiple paths the player can take to reach the real Kraid, the player may never actually come in contact with fake Kraid in a play through. Fake Kraid is similar in appearance but is a darker shade of green and is rather feeble in comparison with the real one. It only takes a small hit to Fake Kraid to finish it off. Unlike the real Kraid, it regenerates if it is destroyed if the player re-enters the room.

Super Metroid
Kraid reappears in Super Metroid in a much larger form, taking up the space of approximately two vertical screens. In this appearance, its body is invulnerable except for his mouth, which opens after Kraid is shot in the eyes. Four Super Missiles, or 20  missiles and/or charge shots, are necessary to defeat Kraid. There is, as in the original, a fake Kraid in this game just before the real Kraid's room though dwarf-like in comparison, both in terms of size and strength. Just like the Metroid decoy, it regenerates if it is destroyed if the player re-enters the room. just outside the room you fight kraid, there apperars to be a dead body that could be another Bounty Hunter

Metroid: Zero Mission
In Metroid: Zero Mission, Kraid is reminiscent of its appearance in Super Metroid, suggesting that Kraid was meant to be gigantic in the original and did not "grow" between its appearances in Metroid and Super Metroid. Worthy of note is that there is no fake Kraid in this game. Oddly enough, the identical room in which it appeared in the original game is present, however, fake Kraid is no where to be seen. Kraid is also given his own area.

Other games

 * Super Smash Bros. Melee: A trophy of Kraid is obtained when the "Brinstar Depths" stage is unlocked. Kraid also appears as part of the stage Brinstar Depths. Occasionally, he will emerge from the magma, roar and rotate the arena by slamming the arena, changing gameplay.

Trivia

 * Kraid was originally intended to make an appearance in Metroid Prime as a boss (link), and was modeled and skinned by Gene Kohler for that purpose. However, time constraints prevented it from being included in the final version of the game. Though the beta model displays him inside Phazon Mines, according to Kohler, he was in fact not replaced by the Omega Pirate. Kraid is referenced, however, in Metroid Prime. One of the tanks in the Space Pirate's base suggests that one of the Pirate's experiments is to recreate the creature. Body parts in the vat appear to be Kraid's. Of note in the Prime Kraid's appearance is his head. It appears to be covered by a metal dome in the picture.