Conductive hydrogels have attracted extensive interest owing to its potential in soft robotics, electronic skin, and human monitoring. However, insufficient mechanical properties, lower adhesivity, and unsatisfactory conductivity seriously hinder potential applications in this emerging field. Herein, a highly elastic conductive hydrogel with a combination of favorable mechanical properties, self-adhesiveness, and excellent electrical performance was achieved by the synergistic effect of aminated lignin (AL), polydopamine (PDA), polyacrylamide (PAM) chains, and biomass carbon aerogel (C-SPF). In detail, AL was applied to induce slow oxidative polymerization of DA for preparing the sticky hydrogel containing PDA. Then, C-SPF carbon aerogel was used as a matrix to construct a dual-network structured composite hydrogel by combining with the hydrogels derived from PDA, AL, and PAM. The as-prepared conductive hydrogel displayed excellent mechanical performance, strong adhesive strength, and repeatable adhesivity. The prepared hydrogel-based pressure sensor possessed fast response (0.6 s loading and 0.8 s unloading stress time), high response (maximum RCR = 1.8 × 104), wide working pressure range (from 0 to 240.0 kPa), and excellent durability (stable 500 compression cycles with 30% deformation). In addition, the prepared sensor also displayed ultrahigh sensitivity (170 kPa–1), which was near 4 orders of magnitude higher than the conventional lignin-modified PAM hydrogels. The multiple interactions between hydrogel components and the mechanical properties of hydrogel were also verified by molecular dynamics investigation. Moreover, the excellent cytocompatibility and antibacterial activity of this composite hydrogel ensured high potential in various applications such as human/machine interaction, artificial intelligence, personal healthcare, and wearable devices.