[en] Observed at z = 4.601 and with $L_{\mathrm{b}\mathrm{o}\mathrm{l}}$ = 3.5$\times <!--\; ??\; -->{10}^{14}{L}_{\odot <!--\; ???\; -->}$, W2246–0526 is the most luminous galaxy known in the universe and hosts a deeply buried active galactic nucleus (AGN)/supermassive black hole (SMBH). Discovered using the Wide-field Infrared Survey Explorer, W2246–0526 is classified as a hot dust-obscured galaxy, based on its luminosity and dust temperature. Here, we present spatially resolved ALMA [C ii]157.7 μm observations of W2246–0526, providing unique insight into the kinematics of its interstellar medium (ISM). The measured [C ii] -to-far-infrared ratio is $\sim <!--\; ???\; -->2\times <!--\; ??\; -->{10}^{-<!--\; ???\; -->4}$, implying ISM conditions that compare only with the most obscured, compact starbursts and AGNs in the local universe today. The spatially resolved [C ii] line is strikingly uniform and very broad, 500–600 km s⁻¹ wide, extending throughout the entire galaxy over about 2.5 kpc, with modest shear. Such a large, homogeneous velocity dispersion indicates a highly turbulent medium. W2246–0526 is unstable in terms of the energy and momentum that are being injected into the ISM, strongly suggesting that the gas is being blown away from the system isotropically, likely reflecting a cathartic state on its road to becoming an unobscured quasar. W2246–0526 provides an extraordinary laboratory to study and model the properties and kinematics of gas in an extreme environment under strong feedback, at a time when the universe was 1/10 of its current age: a system pushing the limits that can be reached during galaxy formation.