As an avid fan of the comics, I'd say that the most powerful mutant wires down to two people:
Jean Grey and Franklin Richards.
Jean, at present, is an EXTREMELY powerful telepath (2nd to only Xavier) and the most powerful telekinetic person in X-Men. She is also capable of some reality-warping capabilities (to an unknown extent).
Franklin Richards (the son of Reed & Susan Richards, from the Fantasitic Four) is a reality-warper of an extreme level. Essentially, anything he can think of, he can make happen. In the Onslaught story, he created an entire "pocket" dimension in order to save his parents' lives. All that, and he's only 12, at best.
Well, I don't know how old he is (why I said "at best"😉. I just say 12 because, unlike his parents, he's a fully mutant (ie, X-gene positive, whereas his parents are metahumans; natural humans that survived an unnatural mutation), so his powers wouldn't activate until puberty, and its been a little while since his activated.
the most powerfull mutant is none of the above
If youve ever read the comics apocalypse is the most powerfull mutant, not even jean greay as the pheonix could stop him it was tried and she was killed near the begining of the age of apocalypse, even though the pheonix cant die well she DID. but if you want to get into lagistics of it all cyclops and jeans baby X-man is the most powerfull he can go toe to toe with the apocalypse and live to talk bout it, but from the category given the pheonix no doubt, and rougue can absorb energies but if she tried absorbing somone like pheonix she would be overcome with power and die GAMBIT is still the best though 💃
ragesRemorse, in the Age of Apocalypse crossover, Jean doesn't have the Phoenix power, nor did she ever. That's what creates one of the conflicts of the Gambit & The X-Ternals comics of the AoA story (Jean never got Phoenix, therefore couldn't fix the M'Kraan crystal). And she didn't die at the beginning. She dies (along with everyone else) in X-Men Omega, the last comic of the AoA story. In the AoA, also, Nate goes toe to toe with Apocalypse, yes, but doesn't finish the fight. That's left to Magneto, who uses his power to literally tear Apocalypse in half, killing him. Great line by Magneto as Apocalypse is dying: "For 20 years, you've gone off on how only the strong survive. Tell me again, Apocalypse, just how strong you are."
X-Man, aka Nate Grey, is technically NOT Jean and Cyclop's kid, he was genetically engineered from their DNA by Sinister in the AoA story, but he crossed over into the proper timeline. Yes, he was immensely powerful, but that was his downfall. Due to his immense power, and hyper-aging by Sinister, he burned out and died some time ago in the comics.
As for Apocalypse, yes, he is immensely powerful (able to alter his molecular structure in any way he wants). Well, he WAS. Apocalypse is dead now, killed by Jean/Phoenix and Cable. It happened in the conclusion of the Apocalypse: The Twelve storyline. In it, Apocalypse needed to possess a new body to continue living, and tried to have it be X-Man/Nate Grey. But, at the last moment, Cyclops pushed Nate aside and Apocalypse possessed him. Some time later, Jean and Cable confronted the Cyclops/Apocalypse being (often referred to by fans as Cyclopalypse). Jean used the Phoenix power to mentally rip Apocalypse very soul out of Cyclops, allowing Cable to attack Apocalypse's astral form. Cable stabbed it with his Psi-mitar (a weapon that attacks astral bodies and also damages metal abilities) and Apocalypse's soul exploded.
As for Rogue, yes she was quite powerful before she recently lost her powers. Due to her touching a Skrull (an alien race), her powers evolved so that she could recall any power she absorbed for use at anytime. That made her extremely powerful. However, she is not able to absorb power from Phoenix. Phoenix is a cosmic force that inhabits a person. Touching that person would only allow her to absorb the powers of that person, not the Phoenix. Still, the person's body would be severely drained from the contact.