Not my work, credit to this thread: https://old.reddit.com/r/communism/comments/k4vbl0/quick_guide_to_debunking_death_toll_claims/

Source: When someone makes a Death Toll Claim, always ask for the source. In most cases the conversation would have ended here as most people who make DTCs are idiots, but in case they persist, you can make a pretty educated guess on their source depending on their DTC.

If they claim any of the following:

• Mao killed 65 million
• Stalin killed 15 million
• Holodomor killed 7 million
• Gulag killed 3 million
• Communism killed over 100 million

Then it is safe to assume that they got their numbers from “Black Book of Communism,” a book that is despised in the academic field. A whole book can be written about why “BBoC” is academic trash but here are some quick trivia to remember:

• Two of the book contributors renounced their association with the book.
• Harvard University retracted its publication of the book.
• The book defines “any unnatural death” concurrent to Communism as a “victim to it.”

If the DTC list includes famine death, but the list itself does not list Winston Churchill’s Death Toll in the millions (3 million based on credible sources), it is safe to assume that this list is bogus and question the OP as to why Winston Churchill, who directly caused the Bengal Famine that killed 3 million people, is not on the list.

How to determine whether a list included famine deaths:

• If the USSR death toll is significantly above 1.8 million
  • 800,000 executions throughout the entire USSR
  • About one million gulag deaths
• If the Maoist China death toll is significantly above 400,000
  • About 400,000 deaths in the Cultural Revolution

I decided to include the gulag deaths for USSR as they are more than simply famine, but still significantly overestimated in most scenarios.

In short, if you see that the DTC is supported either by BBoC or Famine Deaths (in most cases, both), then you have more than sufficient knowledge at this point to debunk them.

Edit: Sources used:

Winston Churchill Bengal Famine Death Toll

Maoist China Death Toll

Holodomor Death Toll

USSR Penal System Death Toll

A commenter posted this, which is very insightful:

One thing to note about Gulag deaths is that many of them prior to the late 1940s were as a result of infection due to antibiotics not being available / invented in the USSR yet. After they were invented and available deaths in the Gulag system dropped significantly. and were even commensurate or lower than prison systems in the United States.

Edit: Sources for this:

American Historical Review Paper documenting death rates This shows a sharp dropoff in deaths around the end of WWII right around when antibiotics became widespread and available in the USSR.

Discovery of Antibiotics in the USSR in 1942 on page 128

This memo by some folks in Sweden explicitly makes this connection (not peer reviewed)

Finally there are some Western Academics that will make the claim that antibiotics were not widely available in the USSR until like the 1980s. This is false. This article notes that by the end of WWII there was enough widespread use of antibiotics that the USSR faced problems with antibiotic resistance at the end of WWII. This only occurs after widespread usage, it would imply that antibiotics were widely available at the end of WWII. Right around the dropoff in deaths.

http://www.biotech-monitor.nl/3905.htm

[...]

As far as I understand it yes between ~300k and 1.5 million German POWs died while in Soviet custody. While some prisoners of war went through the GULAG system most were kept in the GUPVI camps. They also were under NKVD jurisdiction. They had similar conditions to many of the colonies in the gulag system. IIRC there was more of a focus on ideological reformation (since they were Nazis). Due to the similar conditions (lack of effective sanitation, lack of antibiotics, famine). Many also died as a result of infection or starvation as a result.

So some might include those death totals in "Gulag" totals but that would not really be a correct categorization of them.

Another comment:

We must not also forget that the -

1.8 Million people who were killed in the Gulags simply Reactionaries, Counter Revolutionaries and Fascists. Those numbers are also false and exxagerated and in fact the Mortality rates at the Gulag were no different than a Standard Western Prison.

400k people who were killed in the cultural revolution were Landlords who did not obey orders from the PLA to distribute their land and grain and simply reactionaries and counter revolutionaries.

Refer https://qr.ae/pNieIB

Edit:

I thought of mentioning this video. The deaths caused by Communism are narrated by a Centric Manner, explaining that the deaths caused by Gulags or Famines or Massacres won't be counted as deaths by a Socio-Economic system but as Atrocities comitted by someone regardless of if they happened or not. https://www.youtube.com/watch?v=wflMmNTXqKk

Last one:

Funnily enough:

Solzhenitsyn opined on 2 April 2008 in Izvestiathat the 1930s famine in the Ukraine was no different from the Russian famine of 1921 as both were caused by the ruthless robbery of peasants by Bolshevik grain procurements.[110] He claimed that the "provocatory shriek about a 'genocide' was started in the minds of Ukrainian chauvinists decades later, who are also viciously opposed to 'Moskals.'" The writer cautioned that the genocidal claim has its chances to be accepted by the West due to the general Western ignorance of Russian and Ukrainian history.[110]

Solzhenitsyn being the author of "The Gulag Archipelago", also a self-contradicting, ethno-state promoting nationalist. Not that I am trying to bring legitimacy to anything they said, but you can always bring this up and see how they try to reconcile the contradiction between this and their other "evidence".