This is the head of the Mini-Boss hideout in Brinstar. His primary attack consists of hurling spikes from his stomach, horns from his back, hitting things very hard, or grabbing them with his grapple-beam. He can also turn into a ball, but it's generally preferred if he doesn't. Although, given his... girth, you'd think that by simply jumping up and landing on something, that would probably do a fair amount of damage as well.
Kraid has somehow managed to achieve the nigh-impossible. He has thoroughly shown that he's both quite smart yet unbelievably stupid at the same time. Not only has he taken several of Samus' prize powerups, but he has also managed to piss Samus off on many occasions, thus bringing him to the brink of destruction at her hands. He however does have his uses, with his ability to dig almost effortlessly through most surfaces with his claws, but also appears capable of retaining many, MANY names in memory, and if he puts the effort into it, can differentiate between many seemingly identical objects.
He otherwise spends most of his time still hanging around Samus, receiving the occasional missile for being... well... Kraid. When last spotted, he had eaten Mother Brain's heart, stopping the clonatorium from creating another copy of her. And then wandered back to the bar with Samus.