Why was Stalin so evil?

In wrestling, the term heel means villian and usually someone you should boo at when they enter the ring. But let's use heel's wrestling meaning for today's lesson where we ask the question: Why was Stalin so evil? When was his heel turn?

His dad, Besarion was an alcoholic as his shoe business struggled to keep up with the times which coupled with unsuccessful family building attempts (any children the Dzhughashvilis had were either stillborn or died in childhood) left him an angry man who would torment and beat his wife Ketevan "Keke" and surviving child Joseph (who was a bright kid, nicknamed Soso by his mother). Eventually they broke free from his dad and Joseph Stalin became the first in his family to go to school.
He joined a political underground scene and aligned himself with Lenin. He was arrested 11 times since 1900 but always found a way to escape very easily, being known to the law and were promoted were promoted from Lenin in 1912.
He took on the name Stalin as a codename for political purposes from the Russian word for Steel. As a result, his surname meant man of steel. Despite changing his surname to Stalin the family name was still Dzhughashvili. He first got married to Kato Svanidze with who he had 1 child Yakov. Sadly, she died young and Joseph was greatly affected by it so at her funeral, Stalin declared to a friend "This being softened my heart of stone; she passed away and with her have gone my last warm feelings for people".