The former Soviet Union (population):

Russia 🇷🇺 - 144.3 million

Ukraine 🇺🇦 - 37m

Uzbekistan 🇺🇿 - 35.2m

Kazakhstan 🇰🇿 - 19.6m

Azerbaijan 🇦🇿 - 10.4m

Tajikistan 🇹🇯 - 10.2m

Belarus 🇧🇾 - 9.4m

Kyrgyzstan 🇰🇬 - 6.7m

Turkmenistan 🇹🇲 - 6.5m

Georgia 🇬🇪 - 3.7m

Moldova 🇲🇩 - 3.4m

Armenia 🇦🇲 - 2.7m

Lithuania 🇱🇹 - 2.7m

Latvia 🇱🇻 - 1.8m

Estonia 🇪🇪 - 1.3m