To find the greatest common factor (GCF) of the polynomial \(4x^4 + 12x^3 - 36x^2 + 24x\), we first factor out the common terms from each of the coefficients and the variable.
- The coefficients of the terms are 4, 12, -36, and 24. The GCF of these numbers is 4.
- In terms of the variable \(x\), each term contains at least \(x\), so we can factor out \(x\).
Thus, the GCF of the entire polynomial is:
\[ 4x \]
Therefore, the correct answer is 4x.