While achieving the Paris climate goals and sustainable development goals (SDGs) are two major global challenges of our time, energy transition that plays an essential role in achieving climate targets may create socio-economic hardship. A quantitative assessment of the vulnerability of energy transitions is a prerequisite for national and international policymakers to advance a just energy transition that looks after coordination between energy transitions and socio-economic development. This study proposes to measure energy transition vulnerability from the dimensions of exposure, sensitivity, and adaptive capacity. The results of energy transition vulnerability index (ETVI) scores for 135 nations reveal a huge inequality across nations; moreover, the COVID-19 pandemic has interrupted the decade-long continuous improvement of energy transition vulnerability. Developed countries usually have low energy transition vulnerability than developing countries and the gaps even have been widened. The existing global transition vulnerability could be mitigated by 12.3 p.p and 5.2 p.p if each nation could follow the path of global or climate party group frontiers in achieving the SDGs, despite the scale and drivers of mitigation vary across countries. The study also suggests that heterogeneous transition policies that consider both emissions and vulnerability are required. Our framework and findings could advise policymakers to formulate policies and cooperation strategies to reduce vulnerability, protect vulnerable countries, and make fair energy transition policies nationally and internationally.