We report a comprehensive study of the decay cascade of $3d^{-1}$ vacancies of Kr atoms in clusters using coincident detection of up to four electrons and one ultraviolet photon. We find that the intraatomic Auger decays predominantly proceed similarly to the atomic case, with a cluster counterpart identified for each major channel. Most Auger final states are of Kr${}^{2+}4l^{-2}$ or $4l^{-3}nl\prime$ character, with $l=s$ or $p$ and $l\prime =s$ or $d$. In strong contrast to the atomic monomers, where these final states decay radiatively to the ground state, in clusters all Auger final states decay via interatomic mechanisms, namely different, sometimes exotic, variants of interatomic Coulombic decay (ICD), electron-transfer-mediated decay (ETMD), and radiative charge transfer (RCT). Some pathways are enabled only once the clusters reach a minimum size, for example, when an energy transfer involves atoms beyond the first coordination shell. Competition between several interatomic channels and their cascading occurrence is observed. High-energy Auger final states undergo a second Auger step in atoms, leading to Kr${}^{3+}$ states, which is barely observed in clusters, likely due to interaction of Rydberg-like orbitals with neighboring atoms. Our study demonstrates the omnipresence, rich variety, and competition of interatomic processes in this prototype system following the absorption of a single X-ray photon.