The dissociation of the chromium dimer has proven to be one of the most challenging systems for multireference quantum chemical methods, and it has been used to test a plethora of approaches. Due to one 4s and five 3d unpaired electrons in the 7 S ground state of each atom, the chromium dimer has a formal sextuple bond, which requires at least an active space of 12 electrons in 12 orbitals for the description of its dissociation. One of the challenges in this molecular system is the large imbalance of the role that dynamic correlation plays at different inter-nuclear distances. Around the equilibrium, there is a significant overlap between the compact 3d orbitals, and the presence of many electrons in such a small space requires an accurate description of short-range correlation effects. This can be achieved by including a large number of Slater determinants in the expansion of the wave function, leading to a sizable contribution of dynamic electron correlation in this region of the potential energy curve (PEC). On the contrary, a crude description of the Coulomb cusp results in a significant overestimation of the repulsion between the electrons, which explains why the CASSCF PEC is strongly repulsive at short inter-nuclear distances (see Figure in the Supporting Information). The situation is qualitatively and quantitatively different during dissociation, where only the more diffuse 4s orbitals overlap, thereby decreasing the importance and contribution of dynamical electron correlation. Another difficulty encountered in the description of the chromium dimer, which is common to transition metal systems, is the presence of a dense manifold of low-lying electronic states. This makes MRPT approaches, and in particular the CASPT2 method, very susceptible to intruder states. As a matter of fact, the Cr 2 molecule has been the quintessential test of the intruder state problem since the early days of CASPT2, and has been used as a representative system to highlight the effectiveness of both the real and imaginary level shift techniques. In this work we keep this tradition and assess the σ p regularizers on the dissociation of Cr 2 as well. In particular, we adopt the minimal 12 electrons in 12 orbitals active space in association with the cc-pwCV5Z basis set, and include scalar relativistic effects through the second-order Douglas-Kroll-Hess Hamiltonian. The CASPT2 potential energy curve is computed for the lowest singlet state using the modified g 1 zeroth-order Hamiltonian, which provides a qualitatively correct shape of the PEC. All energies are given relative to twice that of the single atom and no correction for the basis set superposition error was considered, as it does not affect the potential existence of intruder states. The variational energy expression, Equation ( ), has been used in all cases unless otherwise stated. As a reference, we report the experimental curve of Dattani 60 in all the plots, which predicts a dissociation energy of 1.66 eV. Note that the main focus of these calculations is not to obtain the best possible ab initio results reproducing the experimental data, but rather to investigate the effectiveness of the regularizers in suppressing the intruder states.