A panel data analysis of the nonlinear dynamics of economic-development in a macroprudential policy regime was conducted in a panel of 25 emerging markets who were grouped together based on their regions: 10 African countries, 8 Asian countries, and 7 European countries covering the period 2000–2019. The paper explored the validity of the Kuznets hypothesis in a prudential policy regime as well as the threshold level at which economic-development reduces inequality, using the Bayesian Spatial Lag Panel Smooth Transition Regression model. This model was adopted due to its ability to address the problems of endogeneity, heterogeneity, and time and spatial-varying in a nonlinear framework. We found evidence of a non-linear effect between the two variables, where the threshold was found to be US$15,900, above which reduces inequality in the African emerging markets; while for emerging Asian and emerging European markets, we documented a U-shape relationship with an optimal level of economic-development estimated at US$17,078 and US$19,000, respectively. Unconventional and macroprudential policies were found to trigger development-inequality relationships. The result supported the S-curve relationship in these regions. Our evidence largely suggests that policymakers ought to formulate policies aiming at increasing agricultural productivity through land redistribution, investment, trade, and promoting human development. Policymakers should also be cautious when implementing macroprudential and unconventional monetary policies.