Cancer research has gradually shifted its focus from individual therapies to a combination of them for enhanced treatment effectiveness. In particular, the increased interest in the field of catalytic medicine through nanozymes proposes promising combinations with photothermal therapy, photodynamic therapy, and magnetic fluid hyperthermia (MFH). Nanozyme activity centers around the hydroxyl radical ˙OH, the most toxic of the reactive oxygen species (ROS). With a synergistic approach in mind, we studied V_xFe_3-xO₄ magnetic nanoparticles (MNPs) as agents for ROS production and heating. These MNPs were exhaustively characterised both morphologically and magnetically. A compositional analysis through electron microscopy and spectroscopy unveils a core-shell structure with a V-rich shell. A study of the power absorption of these MNPs fixed into a gel matrix, emulating cytosol viscosity, provides values of up to 1000 W g^-1 for samples with 0.5 wt% MNPs, an AC magnetic field amplitude of 65 mT and a frequency of 350 kHz, typical in the MFH application. A concentration of the ˙OH-adduct of up to 2300 nM has been measured through electron spin resonance analysis as a result of peroxidase-like activity. Through the comparison with similarly-sized ferrite MNPs, we determined that V incorporation lowers the magnetic anisotropy and serves as an electron buffer, explaining the enhanced MFH and ROS-production results.