The Mott metal-insulator transition is among the most broadly investigated phenomena of correlated electron research – especially in geometrically frustrated materials that promise the realization of a quantum-spin-liquid state. The organic charge transfer salt κ-(ET)2Cu2(CN)3 became the most intensely studied genuine Mott system [1] as it is located at a sweet spot in the phase diagram enabling to examine both frustration effects on its magnetic ground state (ambient pressure) [1-3] as well as the insulator-metal transition (1 – 2 kbar pressure) [3-6]. The latter features first-order phase coexistence [5] as well as an enigmatic bad-metal state with resilient quasiparticles arising from a Fermi-liquid ground state [6]. Here, we perform nuclear magnetic resonance (NMR) and dc transport measurements on the chemical substitution series κ-[(ET)1-x(STF)x]2Cu2(CN)3 spanning from the spin-gapped Mott-insulating state (x = 0) [1-3] to the Fermi-liquid and bad metallic region (x → 1) [5,6]. By probing NMR and dc transport on the same samples over a wide range of correlation strength (equivalent to 20 kbar), we obtain deep insight into the breakdown of coherent charge transport with increasing temperature and correlation strength. Our results imply that the deviations from Fermi-liquid behavior – ρ ∝ T2 and temperature-independent (T1T)-1 – in the bad metal are the consequence of steadily reducing quasiparticle weight Z as temperature increases above TFL. Notably, this trend is opposite to oxides, where Z increases with T [7,8]. References [1] A. Pustogow, Solids 3, 93–110 (2022). [2] B. Miksch et al., Science 372, 276-279 (2021). [3] A. Pustogow et al., Nat. Commun. 14, 1960 (2023). [4] A. Pustogow et al., Nat. Mater. 17, 773-777 (2018). [5] A. Pustogow et al., npj Quantum Mater. 6, 9 (2021). [6] A. Pustogow et al., Nat. Commun. 12, 1571 (2021). [7] X. Deng et al., Phys. Rev. Lett. 113, 246404 (2014). [8] A. Hunter et al., Phys. Rev. Lett. 131, 236502 (2023).