Telekinesis.
Remove all the other abilities that he gained, and Riley will still be at 90% as long as he has his telekinetic abilities. He barely even remembers some of the powers he has—he really truly only needs Alice's ability.
Moving things with his mind was as easy as moving things with his hands, and he could even argue that he had better control of telekinesis than his limbs.
If there was one thing in this universe that he could always identify, it was the use of telekinesis; even if it was just as light as lifting a feather, he would know if telekinesis was involved.
And the force that suddenly pushed him down to the ground when he tried to fly up into the air?
That was undoubtedly telekinesis.
…And it was stronger than his.
