Not true. His powers are known. It's the limits that aren't. And the discrepancy? That's called shitty writers.
http://www.marveldatabase.com/Apocalypse_%28En_Sabah_Nur%29
As you can see, he's got some crazy ass powers. He was Alpha level before the celestials enhanced him.
Going through these lists of his feats, from the links posted by xplosive. Apocalypse does numerous things that isn't said on the marvel database or anywhere els, such as, detach his head from his body and fly it around ( 😆 ) transmute his body by creating a liquid cure from it. Apparently, able to manipulate time. And your trying to tell me that his powers are not fully identified?
Well, I'm gonna try and post some feats of Apoc.
Laughs off a big High Evolutionary blast, it doesn’t effect him.
htp://i2.photobucket.com/albums/y37/Nightmareman95/powers1.png
Defeats The X-Men under sixty seconds.
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Takes X-Factor, the Inhumans, Askani/Rachael Summers, and Charlotte Jones w/big tech gun- hitting him with everything they had to no effect, he waded through it.
htp://i2.photobucket.com/albums/y37/Nightmareman95/powers4.png
Takes Cyclops’ full power blast like nothing hit him. And sucks him bone dry of energy.
htp://i2.photobucket.com/albums/y37/Nightmareman95/powers6.png
Again, takes on Cyclops' optic beam with no effect on him, even in his weakened state woken from his sleep too early.
htp://i2.photobucket.com/albums/y37/Nightmareman95/powers5.png
The Invisible Woman puts a forcefield around him so he can’t move, yet he then moves, she tries to block his blast with her forcefield, and it shatters. To my knowledge her forcefield has never been shattered before, nevermind broken twice in a row so easily.
htp://i2.photobucket.com/albums/y37/Nightmareman95/powers7.png
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Reads Ozymandias’ mind of all the events that happened since X-Ecutioner’s Song in a moment.
htp://i2.photobucket.com/albums/y37/Nightmareman95/powers10.png
Restraining the Hulk with one arm (note that this was 616 Hulk during Heroes Reborn, who was tapping into the energies of the HR pocket reality and other dimensions, very strong, but was less durable than usual). Apocalypse did have leverage on his side there in dragging him, but he got The Hulk into that position in the first place and the Hulk couldn’t break free.
htp://i2.photobucket.com/albums/y37/Nightmareman95/powers11.png
Fights Prime Eternal Ikarus. His punch waylays Ikarus, while his bearhug proves inescapable to Ike.
htp://i2.photobucket.com/albums/y37/Nightmareman95/powers12.png
htp://i2.photobucket.com/albums/y37/Nightmareman95/powers13.png
Fights the norse god of lies and mischief himself. Loki needs to put effort into breaking free from his one handed grip (notice his facial grimace). Loki is estimated to be between class 50 and 70, so he’s a strong guy.
htp://i2.photobucket.com/albums/y37/Nightmareman95/powers15.png
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Creates a forcefield able to hold even pre-powerdown Exodus.
http://i2.photobucket.com/albums/y37/Nightmareman95/powers18.png
Reality warps Ozymandias from normal man into a being of pure stone that can move like a man.
http://i2.photobucket.com/albums/y37/Nightmareman95/powers19.png
Phased his hand into The Harbinger, then re-arranges his insides (matter re-arrangement, or reality warping or something, not sure) to turn him from an unlimited instantaneous adapter/evolver into a living mega bomb with the powers he already had developed. He will destroy New York City when he explodes.
http://i2.photobucket.com/albums/y37/Nightmareman95/powers20.png
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A weakened Apocalypse’s single blast meant for humans, weakens Jean Grey after hitting her forcefield (heck it even knocks himself over)
http://i2.photobucket.com/albums/y37/Nightmareman95/powers22.png
Clocks a super speed running Quicksilver.
http://i2.photobucket.com/albums/y37/Nightmareman95/powers23.png
Some more of Apocalypse fightning the High Evolutionary. The fact that he first not only laughed off High Evolutionary's energy blasts but also stalemated the near godlike geneticist, and in the end forces him to listen what he has to say. Is indeed impressive.
http://i2.photobucket.com/albums/y37/Nightmareman95/powers1.png
http://i2.photobucket.com/albums/y37/Nightmareman95/powers24.png
http://i2.photobucket.com/albums/y37/Nightmareman95/powe25.png
http://i2.photobucket.com/albums/y37/Nightmareman95/powe26.png
This is interesting. He's able to see Uatu The Watcher when he’s cloaked himself from everyone else.
http://i2.photobucket.com/albums/y37/Nightmareman95/powe27.png
Whoa! Time manipulation.
http://i2.photobucket.com/albums/y37/Nightmareman95/powe28.png
http://i2.photobucket.com/albums/y37/Nightmareman95/powe29.png