The US is the only superpower that has used WMDs on an enemy
Assuming we’re talking about biological or chemical weapons, that’s not true.
https://en.wikipedia.org/wiki/Rhodesia_and_weapons_of_mass_destruction
During 1976 members of the Selous Scouts disseminated V. cholerae in the Ruya River. The unit also used the material to contaminate the water supply of the town of Cochemane in Mozambique. Deaths from cholera occurred in both areas
https://en.wikipedia.org/wiki/Iraqi_chemical_attacks_against_Iran
According to a 2002 article in the Star-Ledger, 20,000 Iranian combatants and combat medics were killed on the spot by nerve gas. As of 2002, 5,000 of the 80,000 survivors continue to seek regular medical treatment, while 1,000 are hospital inpatients.
https://wcfia.harvard.edu/publications/forgotten-gas-attacks-yemen-haunt-syria-crisis
Forgotten Gas Attacks in Yemen Haunt Syria Crisis
Americans might lead the world in the use of WMDs, but they are not acting alone.