Apocalypse's full extent of powers remain to be revealed, especially to the extent of which powers have since been augmented by alien technology. Apocalypse claims to have control of his body on the molecular level-- allowing him to shape change and elongate with virtually unlimited range, to increase density and allow his body to mimic metals and armors, to teleport, and to be virtually immune to the effects of age. Apocalypse can also increase his strength to levels surpassing that of the Hulk, grow to giant sizes, and gain the power of flight, sometimes through turning his arms into wings or jets. Apocalypse can also transform himself into a variety of human disguises.
He has exhibited energy absorbing and projecting abilities in the past. Apocalypse has been termed an "External," due to his mutant ability of immortality. Briefly, Apocalypse has shown potential to be a powerful psionic.
It has further been hinted that Apocalypse's body is ravaged by a techno-organic disease. Many of his regenerated bodies must use an exoskeleton body armor to prevent his energies from consuming him. Apocalypse can apparently merge/switch host bodies to continually revive his self-consuming body.
Onslaught possessed the combined abilities of Professor X, Magneto, Franklin Richards, and X-Man, including telepathy, telekinesis, astral projection, illusion creation, mental bolt projection, sensing mutant presences, manipulating magnetic fields, and affecting reality itself. Onslaught could also enhance its physical size and strength.