Power Mimicry is the ability to mimic and copy the powers of others around oneself. This is down from touch or just absorbing the nearby energy signatures. They can mimic the psychic energy outputs, genetic structure or superhuman physiology that enable abilities in other people. User can even stack several powers together.
Mimic (Calvin Rankin) is able to copy the knowledge, skills, and powers (if any) of every individual within a certain range of him; different sources list this as anywhere from several feet to a mile radius. This applies to both superpowered and "normal" abilities, as shown when he duplicated athletic skill on the football field in high school. He has shown the capacity to manifest numerous powers at the same time, and since he also absorbs knowledge, he can immediately use copied powers with the same skill level as the original owner. However, he occasionally shows difficulty in juggling multiple powers, and his body can be overloaded by absorbing too many at once. Usually the Mimic loses his duplicated abilities once out of range of the owner, but theoretically due to the length of time spent with them, his body can permanently retain the powers he mimics.
The Mimic of Earth-12 has different specifications for his abilities. Calvin Rankin of the Exiles can only mimic five power sets at once, each at only half the potency of the original source. He can instantly mimic the powers of another temporarily, but must remain in the presence of the source to retain these powers. After a period of time, between 30-60 minutes, Mimic will have retained the borrowed powers long enough that he can choose to retain them permanently, until he wishes to discard them.
The Super-Adaptoid was a android that could copy the powers, appearance, and equipment of any superpowered being in close proximity to it. It was created by A.I.M. (Advanced Idea Mechanics) who incorporated a portion of a Cosmic Cube into it. It can duplicate any being, visually indistinguishable from it. Given the opportunity, it can copy up to eight different beings at one time, combining their attributes in a seemingly random fashion, but all these attributes turn green. The main picture, for instance, shows the Adaptoid with Captain America's shield, Thor's chest medallions, and Iron Man's ribbed armor.
Norman Osborn was given the powers of the Super-Adaptoid thanks to a procedure performed by Monica Rappaccini. As the Super-Adaptoid, Osborn can copy the powers, of any super powered who he manages to touch. However, unlike other super adaptoids he can not duplicate weapons and appearances, leaving only the powers. Given the opportunity, it can copy up to eight different beings at one time. If he touches too many super-humans, he would overpower and stay in a coma. His abilities given to him via the Bio-Adaptoid process are so powerful, he can absorb the Hulk's power as well as copy many others at the same time.
Rogue can absorb the powers, energies, memories, knowledge, talents, personality and physical abilities (whether superhuman or not) of another human being (or members of some sentient alien races) through physical contact of her skin with the skin of the other person. She is not limited to absorbing superhuman abilities: for example, she has absorbed the strength, agility, and sharp reflexes of an enhanced human. She can also absorb psionic abilities. In absorbing another person's memories Rogue also gains the emotional responses connected to them. For the transfer of abilities to be accomplished, Rogue’s skin must contact the skin of her victim. Rogue can only absorb abilities and memories from living organic beings. She can possess the powers of several superhuman persons at once.
No upper limit has yet been determined for the number of superhuman beings whose power she can maintain simultaneously, or for the amount of power that she can absorb. Rogue can even absorb gross physical characteristics from a victim. Her physical appearance does not change when she absorbs abilities and memories from a normal looking human being. The victim's abilities and memories are absorbed for a time sixty times longer than the period of time Rogue was in physical contact with that person. Those touched are rendered unconscious by contact with her, though some beings, including Juggernaut and Mojo have resisted this effect. While for most of her life, her use of this power was involuntary, Rogue has recently gained full control over it.
Hope Summers can psychically duplicate the power-signature of mutants physically near her, and use the duplicated power in its most powerful form. Although she does require close proximity to subjects, she does not need to physically touch them (as with Rogue), nor does it appear as though her using a subject's powers deplete their own power level. Additionally, Hope can duplicate multiple power-signatures concurrently with seemingly no limit. However, her duplicated powers fade due to time, distance, and usage. She is only able to duplicate mutant powers, not those of other metahumans. The upper-limits of her powers have yet to be reached or determined.