What you read about Stalin in western textbooks comes from Nazi propaganda recycled by CIA and MI6. More realistic picture is presented in Ludo Marten’s book Books - The Revolutionary Communist Progressive Labor Party
Imperialist powers hate Lenin and Stalin because they saved Russia from division and colonization by western powers that had already enslaved entire planet. In February 1917 a coup sponsored by England and France overthrew Russian czar and installed a puppet “government” that led Russia to catastrophe. Western puppets destroyed Russian army at the peak of WWI. Corruption and separatism were rampant.
Lenin and Stalin suppressed the liberal coup, restored manageability of country, recreated Russian army, fought and defeated colonial armies sent by England, France, Romania, Japan, the US, Poland, Finland and their local mercenaries that tried to rip Russia into colonies. Lenin and Stalin restored independence and territorial integrity of Russia.
There is plenty of propaganda nonsense in other answers, like Soviet industrialization was carried out by “slave labor”. This is a myth of Nazi propaganda. The point of propagandists is that the 5 fold increase of industrial output was achieved by the labor of prisoners. In the reality the number of prisoners in the USSR ranged from 250 thousands to two millions during the 30s. It is 0.125% - 1% of population. Even at the highest level in 1937–1938 the number of prisoners was comparable to that in modern US.
In Stalin’s time 75% illiteracy turned into 100% literacy. Life expectancy grew from 27 to 65 years. Millions got jobs in science, technology and engineering.
Stalin is co hated by western colonial powers because the USSR serves as an example of independent industrialization. The USSR showed that non-western nation can not only defend itself against western colonial war, but also defeat the imperialist west in a war. The USSR had shown that science, engineering, universal health care and education is possible without colonial slavery. Of course the imperialists from Churchill and Hitler to Truman and Reagan spread slanderous lies about the USSR and Stalin who dealt a deadly blow to the myth of invincibility western imperialism and gave hope to humanity.