Higher slope magnitude in Scatchard plot indicates
The absolute value of the Scatchard slope equals 1/Kd. Consequently a larger magnitude of the (negative) slope corresponds to a smaller Kd and therefore higher binding affinity. This direct visual readout of affinity is one of the principal advantages of the Scatchard transformation when comparing ligands or receptor preparations under identical experimental conditions.
Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)