A one-step synthesis of sheet-like RuS₂ nanoarchitectures exhibiting traits of a potential cathode material for designing high-performance asymmetric supercapacitors (ASCs) is demonstrated. The synthesis includes direct sulfurization of RuO₂ in an inert atmosphere at high temperature that results in densely packed nanosheets of RuS₂ with moderate surface area. Such a structure provides abundant sites for surface or near-surface based faradaic/non-faradaic reactions for energy storage while facilitating ion migration during charge/discharge processes. Benefitted from these traits, RuS₂ electrode exhibits substantially enhanced capacitive performance as compared to the RuO₂ electrode. Detailed analyses suggest that the charge storage in such RuS₂ nanosheets is governed by capacitive as well as diffusion-controlled processes at lower scan rates but is dominated by capacitive processes at higher scan rates. The assembled activated carbon//RuS₂ ASC with an optimum cell voltage of 2V in aqueous electrolyte exhibits attractive energy-power combination with excellent cycling performance, which outperforms many other recently reported ASCs.