Lion
Lions currently occupy a diminishing range across sub-Saharan Africa and a small population in India's Gir Forest. Total wild lion population has declined to approximately 23,000 individuals, restricting the species' threat radius considerably. The Geneva Wildlife Distribution Index estimates that lions pose a credible threat to less than 0.3% of the global human population.
For most humans, a lion encounter requires deliberate travel to specific geographic locations, significantly limiting the animal's reach.
Hangover
The hangover operates without geographic restriction. Wherever alcohol is consumed—which encompasses virtually every nation on Earth—the hangover follows. The World Health Organisation estimates that 2.3 billion people are current drinkers, all of whom fall within the hangover's potential catchment area.
The hangover has even adapted to modern travel, producing a synergistic horror known as the jet-lag hangover that compounds dehydration with circadian disruption.
VERDICT
Simple mathematics favour the hangover overwhelmingly. Whilst one must travel to encounter a lion, the hangover will travel to encounter you, regardless of location, nationality, or socioeconomic status. The hangover's democratic ubiquity secures this criterion.