You think you're tough until H₂S enters the chat! While onions make you tear up with their mild sulfur compounds, hydrogen sulfide is the final boss of eye-watering chemicals. At just 10 parts per million, this rotten egg gas triggers your eyes to water uncontrollably—and at higher concentrations, it can literally shut down your respiratory system faster than you can say "periodic table." Chemistry doesn't care about your bravado, it just wants to watch the world burn (or in this case, cry)! Fun fact: your body produces tiny amounts of H₂S as a signaling molecule, but apparently not enough to build up an immunity to its tear-jerking powers!