What determines the Abilities of a Contractor? What determines the abilities of a Contractor?  In the anime two contractors have the same ability.  Both dealing having the powers of electricity.

So does this mean that there can many contractors with the same ability?
It seems to be randomized as to what kind of power you get. If you could "pick" your power, every Contractor would logically choose things like shooting giant laser beams. Same with the remuneration, although it sometimes seems to be things that the Contractor hates, like the woman who hates smoking who had to eat cigarretes.