Can only restrain someone with telekinesis if they're less than half as strong as him

Another point worth mentioning is regarding Cell's telekinesis. At first he had to use his hand to hold her in place, but by using his strongest hold he is able to actually fight Goku while still maintaining his link on her. The imprisonment can only be broken by Cell losing his focus or by an attack stronger than the telekinetic barrier. And Cell couldn't use this on just anyone, they'd have to be much weaker than him for it to be able to work. Right now 18, Trunks, and Gohan are all less than half his strength, which makes telekinetic holds more than possible.

- Bringer of Death Chapter 51