There is no substitute for the testimony of actual victims of communist terror. However the following films can help to bring to life aspects of Communism and its history. Please be aware that most of these films are based on facts and things that happened but they are fictionalised and not factual accounts.
8. Life and Fate. Excellent Russian TV series based on a celebrated novel. Primarily focussed on the Battle of Stalingrad but with stories of women who have sons, lovers and husbands in the battle, a scientist accused of being politically unsound and the activities of the NKVD. IMDb rating 7.6. Amazon Prime Video.
9. Good Bye, Lenin! Gentle comedy. A young man works hard to pretend to his unwell mother that her beloved Communist East Germany continues whereas in fact the Berlin Wall has fallen. IMDb rating 7.7 Available as DVD and on Amazon Prime Video. Trailer: https://www.youtube.com/watch?v=u5hzmwGW4Ac
10. Child 44. Violent drama set in the Stalin era in which a Russian military police officer investigates a series of child murders. IMDb rating 6.5. Available on DVD and through Amazon Prime Video. Trailer: https://www.imdb.com/title/tt1014763/videoplayer/vi1915792921?ref_=tt_ov_vi
The Irony of Fate (or Enjoy Your Bath). Delightful romantic comedy. A classic in Russia watched repeatedly. IMDb rating 8.3. DVD available.
This is not a trailer but an idiosyncratic introduction to the film: https://www.youtube.com/watch?v=93r23NYla_E
Notes: There is a lack of available films set in Communist China which is unfortunate since China had the highest number of deaths under Communist rule.
The above films are just a small selection of films relating to the Communist era. There are plenty of others worth seeing such as Milada and Mr Jones.