Top-left panel: X-ray EPIC spectra (data) and relative best-fit power-law models modified by intrinsic absorption (dashed lines) and in the lower plot the residuals, i.e., data minus best-fit models. Blue, green, and orange colors refer to the pn, MOS1, and MOS2 detectors, respectively. Energies are reported at the rest-frame. Right panel: α_ox vs L₂₅₀₀. SMSS J2157 is reported as green star, while green, red and blue colors indicate a compilation of type 1 AGNs (Lusso & Risaliti 2016), bright UV-selected quasars (Nardini et al. 2019), and optically/IR selected bright QSOs from the WISSH sample (Zappacosta et al. 2020), respectively. Solid and dashed black lines report the relations inferred by Lusso & Risaliti (2016) and Martocchia et al. (2017).