Self-intercalation in transition metal dichalcogenides (TMDs) offers a unique strategy for doping and spin ordering that preserves structural integrity, minimizing lattice distortions. This modification introduces additional electron density, spin states, and potentially spontaneous superlattice formation. Combining with further high-pressure modulation, more quantum phenomena could be induced for new physics exploration. Here, we present a high-pressure study of the self-intercalated compound ${\mathrm{V}}_{1/4}{\mathrm{VS}}_2$, where antiferromagnetic order arises from $3d$ electrons localized on the vanadium atoms intercalated between the layers. Under pressure, these localized electrons progressively delocalize, leading to the suppression of the antiferromagnetic order and the emergence of non-Fermi liquid behavior near 9 GPa, signaling an antiferromagnetic quantum critical point. Under higher pressure, a Lifshitz transition-induced superconductivity is observed, while the crystalline symmetry remains preserved up to 104.4 GPa. Notably, this marks the first observation of superconductivity in a self-intercalated TMD under pressure. These findings highlight ${\mathrm{V}}_{1/4}{\mathrm{VS}}_2$ as a model two-dimensional system for exploring pressure-induced quantum criticality, electronic topological transitions, and related nontrivial superconductivity, paving the way to new physics by fully exploring the potential of self-intercalated TMDs.

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• Critical phenomena
• High-pressure studies
• Magnetic phase transitions
• Superconductivity
• Strongly correlated systems