\(\left(x-2\right)\left(x+2\right)\left(x^2+2^2\right)\left(x^4+2^4\right)\left(x^8+2^8\right)-x^{16}\)
\(=\left(x^2-2^2\right)\left(x^2+2^2\right)\left(x^4+2^4\right)\left(x^8+2^8\right)-x^{16}\)
\(=\left(x^4-2^4\right)\left(x^4+2^4\right)\left(x^8+2^8\right)-x^{16}\)
\(=\left(x^8-2^8\right)\left(x^8+2^8\right)-x^{16}\)
\(=\left(x^{16}-2^{16}\right)-x^{16}\)
\(=x^{16}-2^{16}-x^{16}\)
\(\left(-2\right)^{16}=65536\)