<p>Laser-driven near-infrared II (NIR-II) light sources comprising luminescent ceramics represent a promising research frontier, yet their development remains constrained by the external quantum efficiency (EQE) and thermal stability bottleneck of current luminescent materials. Herein, we present a non-equivalent cation substitution strategy to fabricate high-efficiency translucent MgO:Ni²⁺, Cr³⁺ NIR-II luminescent ceramics. The co-doping of Cr³⁺ induces structural distortion at Ni²⁺-occupied octahedral sites, effectively breaking the parity-forbidden d-d transition constraint while enabling efficient energy transfer from Cr³⁺ to Ni²⁺. These synergistic effects yield remarkable internal and external quantum efficiencies of 61.06% and 39.69%, respectively. The developed ceramic demonstrates exceptional thermal management capabilities with 31.28 W·m⁻¹·K⁻¹ thermal conductivity and 92.11% emission retention at 478 K. When integrated into laser-driven NIR-II light sources, the system achieves record-breaking performance of 214 mW output power under 21.43 W/mm² blue laser excitation. Practical demonstrations showcase superior non-destructive imaging capabilities with 5.29 lp/mm spatial resolution and 0.97 contrast ratio. This work establishes a new paradigm for developing high-performance NIR-II light sources in advanced imaging and detection technologies.</p><p></p>