Complex sentence: Even before his abilities manifested, Nick had an exceptional ability to make quick and accurate deductions about the motivations and pasts of individuals, which has now expressed itself as his ability to perceive the supernatural that nobody else can see.
Split into simpler sentences: Even before his abilities manifested, Nick had an exceptional ability to make quick and accurate deductions about the motivations and pasts of individuals. This power has now expressed itself as his ability to perceive the supernatural that nobody else can see.