Herein, lignin-rich KOH-activated porous carbon from eucalyptus wood (named as PACE) is presented as an efficient electrode for supercapacitors (SCs). Compared with the most commonly used higher activation temperature, i.e., 800 °C with KOH (PACE-800), a more efficient SC is developed by activating carbon with KOH at lesser temperature, i.e., 600 °C (PACE-600). The high specific capacitance (i.e., 230 F g⁻¹ at 1 A g⁻¹ measured in a 2 m NaCl electrolyte) measured by galvanostatic charge–discharge (GCD) studies is not primarily due to larger surface area, but due to the inherent electron-rich oxygen-based functionalities that persist at the lower activation temperature, contributing to the hydrophilic nature to PACE-600. The mechanism of the capacitive charge storage is deduced from electrochemical impedance spectroscopy (EIS). The application of PACE-600 as a SC electrode is confirmed from insignificant loss in the specific capacitance after 10 000 charging–discharging cycles, recorded at 10 A g⁻¹. Further, fabrication of higher-voltage (1.6 V) symmetric SC PACE-600//PACE-600 in aqueous neutral electrolyte (2 m NaCl) is presented, which illuminates a red LED (1.8 V) for 1 min after charging for 5 s. The corresponding energy density is calculated to be 41 W h kg⁻¹, and at a power density of 2396 W kg⁻¹.