The Impossible Man has complete control over his body’s molecules, allowing him to instantaneously change form at will into anything he can imagine; there seems to be very little limit to the size, shape or form, though he cannot duplicate the abilities of uniquely powerful objects such as Thor’s hammer, and he is unable to change color from his native green and purple; as he originally seemed capable of this, it may be that he was formerly able to do this, but lost the ability when Poppup was destroyed. He makes a popping noise whenever he changes. He can travel through hyperspace and survive in a vacuum. He can reproduce himself by dividing into two identical beings. His mind is difficult for human telepaths to fathom.
http://marvel.com/universe/Impossible_ManTo clarify, Impossible Man CAN mimic superpowers, but not the powers of objects. If he turns into a "Hulk", he'll have the super strength. If he changes to a "Thor" it's a similar thing, but he won't be able to throw the hammer (though his fists could become like hammers and the like).
Adam Warlock possesses a number of superhuman properties and powers derived from his artificially determined genetic structure. His bone and muscle tissue is denser than human, endowing him with superhuman strength and resilience. Among his body's special adaptations are an enclave of cells able to tap and transform cosmic energy for personal use. Warlock could use this energy to enhance his physical strength, endurance, and powers of recuperation. He could also employ cosmic energy to negate the force of gravity beneath him, enabling him to fly. In an Earth-like atmosphere, Warlock was able to attain the speed of sound (770 miles per hour). He could use his cosmic energy to locate and enter natural space-warps (discontinuities in the fabric of space) in order to traverse interstellar space. He can also project cosmic energy from his hands as concussive force.
Warlock's energy-manipulating powers waned at the time he was given the soul-gem by the High Evolutionary. No longer could he direct concussive force from his hands or enhance his strength. Whether this power limitation was caused by his symbiotic relationship with the soul-gem or some other factor is not yet known. When Warlock was summoned from the soul-gem to defeat Thanos, he seemed to possess these cosmic powers once more.
He is is able to spin a cocoon around him at will in a matter of seconds. He did so infrequently during his short life, usually to protect himself from mortal harm, and usually he would emerge from the cocoon at a further level of physical or mental maturity. It is not known where the substance of the cocoon came from, or where it went after he emerged from it.
Warlock gained a great deal of first-hand experience at hand-to-hand combat over the course of his life, and eventually became quite formidable. Warlock also is an accomplished self-taught philosopher.
Warlock also possesses The Soul Gem, an Infinity gem that endows the user with the power to sense the souls of others and draw them into a dimension contained within the gem.
http://marvel.com/universe/Warlock,_Adam