Kraid as he appeared in Super Metroid.
Kraid is a fictional alien monster from the Metroid video game series, resembling the Japanese monster Kaiju. With a fat, bloated reptilian appearance Kraid is one of the biggest as well as largest monsters that Samus Aran encounters. He appears as one of the two minibosses that appear in the NES/Famicom Disk System original Metroid, the other being Ridley. Kraid's main attacks are firing spikes from his belly as well as spinning claws from his fingertips.
Profile
Almost nothing is completely known about Kraid himself. Whereas Ridley would be considered highly intelligent, no data has been given regarding Kraid's mental abilities. Fan work often depicts Kraid being the lesser intelligent of the two. The Space Pirates often use Kraid as a guardian to defend items or locations of significance with his intimidating size, impregnable hide as well as his ability to fire countless organic projectiles, he fulfills this role well.
Metroid
In Metroid, Kraid is the boss of Hideout I, commonly referred to by many fans at the time as simply "Kraid's lair". His design differed considerably from that of later installments. In addition to his smaller size, Kraid sported light brown skin and an illustrious Maine of green fur that ran down the length of his back. Originally, Kraid had two eyes instead of his usual three. Upon his defeat, Samus receives 75 missiles.
There is a decoy Kraid that Samus may encounter before terminating the real Kraid. However, due to the fact that Kraid's Lair has multiple paths the player can take to reach the real Kraid, the player may never come in contact with the fake Kraid. This fake Kraid is similar in appearance to the real Kraid but has darker brown skin with light blue fur and is rather feeble in comparison to the real Kraid. Fake Kraid will regenerate after it is destroyed and Samus returns to the same room.
Super Metroid
In this game, Kraid appears much larger than he does back in the original Metroid, taking up the space of two vertical screens. Now, Kraid is completely impervious, with exception for his mouth, in which Samus can fire missiles in after Kraid is shot in his third eye. As in the original, there is a fake Kraid in this game though dwarf-like in comparison, both in terms of size and strength. Just like the clone in Metroid, it regenerates if it is destroyed and the player returns to the same room. There is a possibility that this Kraid may be a reference to its smaller size in the original Metroid, perhaps indicating Samus merely killed a larval Kraid.
Upon Kraid's defeat, Samus earns the Varia Suit upgrade.
Metroid: Zero Mission
Kraid has been drastically changed in Metroid: Zero Mission in comparison to his original debut. He sports a more round body and a blue-green coloration as opposed to his paler green scales and slightly slimmer body type in his last appearance. His head is now less elongated and connects seamlessly to his neck. In terms of size Kraid is now consistent with his height in Super Metroid which is perhaps a retcon of the actual boss size in the original Metroid. The boss fight itself now closely resembles the Super Metroid fight. Also of note is the lack of a "Fake Kraid" enemy type in Zero Mission in comparison to the original.
Upon defeating Kraid, Samus earns the Speed Booster-- an item that was not in the original Metroid.
Super Smash Bros Melee
Kraid appears in Super Smash Bros Melee, in which he is an obstacle in the Brinstar Depths level. He will pop-up from lava, roar and then whack the rock with his claws, trying to make the combatants fall. Kraid has his own trophy in the game which shows his full model; it resembles his design in Super Metroid but has some slight differences. He is seen with luminescent white eyes as opposed to his usual dark red eyes. His head size was shortened and it now seamlessly connects to his neck which was later seen officially in Metroid: Zero Mission.