The Soviet Union became a great power after the Second World War. The Soviet economy was then more developed than the rest of the world except for the US. It had a complex communications network, vast energy resources including oil, iron, and steel, machinery production, and a transport sector that connected its remotest areas with efficiency. It had a domestic consumer industry that produced everything from pins to cars, though their quality did not match that of the Western capitalist countries. The Soviet state ensured a minimum standard of living for all citizens, and the government-subsidized basic necessities including health, education, childcare, and other welfare schemes. There was no unemployment. State ownership was the dominant form of ownership: land and productive assets were owned and controlled by the Soviet state.

Which constituent country of the USSR dominated it completely which made the people of other regions feel neglected and suppressed?

Russia

Although on paper, Russia was only one of the fifteen republics that together constituted the USSR, in reality, Russia dominated everything, and people from other regions felt neglected and often suppressed.