X-ray luminosity versus column density for different populations of AGNs: optically selected Type-1 QSOs at z = 1.4 − 4.5 (blue symbols; from Just et al. 2007; Martocchia et al. 2017), dust-reddened QSOs at z = 0.4 − 3.2 (green symbols; from Urrutia et al. 2005; Banerji et al. 2014; Mountrichas et al. 2017; Goulding et al. 2018; Lansbury et al. 2020), DSFGs at z = 0.3 − 5.2 (yellow symbols; from Wang et al. 2013; Corral et al. 2016; Zou et al. 2020), Hot DOGs at at z = 1.0 − 4.6 (violet symbols; from Stern et al. 2014; Assef et al. 2016; Ricci et al. 2017; Vito et al. 2018a; Zappacosta et al. 2018), X-ray selected AGNs in the Spiderweb and SSA protoclusters (z = 2.2 − 3.2, orange symbols, Ivison et al. 2019; Tozzi et al. 2022a; Monson et al. 2023), and X-ray selected AGNs in the Chandra deep field-south at all redshifts (gray symbols, with median error bar showed in the bottom-right corner of the plot; from Li et al. 2019). The X-ray selected AGNs in SPT2349–56 and DRC are plotted as red stars and squares, respectively. C1 and DRC-2 (Vito et al. 2020) have remarkably similar physical properties. Their X-ray luminosities are similar to those of luminous optically selected QSOs, but obscured by gas column densities even thicker than those of hot DOGs.