The Summers-Grey Gene Theory of Mr. Sinister
Mr. Sinister had some kind of obsession with Cyclops and Havok but mostly Cyclops, and other obsession was Jean Grey. He already had theorized and maybe even discovered that any child born out from the genetic material of Cyclops and Jean Grey will be one powerful mutant. I always thought about it that he had that in mind when the Jean Grey clone awakened thanks to the Phoenix.
Cyclops' mutant characteristics are as follows. He can absorb ambient energy from his surroundings and store them into his cells. While Havok absorbed cosmic energy, Cyclops absorbed ambient energy. Ambient means from his surroundings which was probably why Mr. Sinister had a greater interest in Cyclops. Cyclops' powers may not be that much of a global destructive force but serves as an "enhancer".
On the other hand Jean Grey was a powerful psionic mutant. She possessed telepathy and telekinesis. Her telepathy did more than read minds, she can also copy thoughts and manipulate them, even create telepathic force blasts and control others. Her telekinesis can also create force fields, levitation and even lift very heavy objects. Also Mr. Sinister created Madelyne Pryor as an experiment to figure out Jean Grey's potential but labeled her as a "failure". Cable got his telepathic powers from the Jean Grey DNA that Madelyne Pryor possessed.
So here's my theory behind any Cyclops/Jean Grey or in Cable's case Cyclops/Madelyne Pryor (who is genetically identical to Jean Grey) offspring have that high level of psionic power. I could be wrong but it's possible that Cable, Stryfe, Rachel and Nathan Grey all absorb ambient energy and store it into their cells, which in turn boosts their psionic powers. Cable's powers manifested even when he was still a baby. I guess the combination of ambient energy absorption plus psionic energies would create such powerful psionic related powers. So powerful that Cable could even survive the T-O Virus that Apocalypse infected him with.