Intelligence: Nexus has extreme intelligence and can build almost anything. With a few exceptions.
Nexus's mechanical arm has many functions, including the rare ability to digitize anything. Even though he can use this ability for anything, Nexus tends to use this ability to digitize and store Astromechs.
Thinking with Portals:
Another function of Nexus's arm is the ability to create 5 sets of Aperture Science Portals.
Death of Nexus James Riles I
When Nexus was 6 years old, his father died. This caused him to devote the rest of his life to completing his father's work.