In general in the west things that are done by the western nations are either ignored, spun as not as bad, or treated like "its history we changed" while they act as if socialists are pure evil. I think you were just experiencing that cognitive dissonance they got mad at you for pointing out their hypocrisy.

The events that are the least emphasized are those that were carried out by dominant powers, particularly when they are still around today writing the history and propaganda books. The way events are handled is seemingly subtle, and the most powerful way they avoid emphasis is to simply never frame the violence they did in terms of its most wide impacts.

For example, you mentioned that you are from India. The greatest violences done to India in the last few hundred years were from the Raj, so the British. And those greatest violences were not the actual acts of ships and soldiers, but in things like this:

• Dismantling of industry and craftmanship in the subcontinent, converting production to the schemes of empire. Namely, producing crops like cotton to supply a British industrialized textile monopoly. This directly created poverty where before there was immense high-value production.

• Famines caused by extreme poverty and the imposition of imbalanced production where farmers had to farm export crops and even export food crops when there were famine risks. The British also did this to Ireland and other colonies.

• The less-talked-about but still incredible violence of poverty in general. Placing a hold on industrialization also meant no balanced infrastructure for the greater public (only what served export and British control), limited hospitals, poor education, more frequent death of one's children, and so on.

• The tweaking of caste to be more racist and classist (per English tastes), creating internal strife and misery.

• Emphasizing other ethnic divides to use marginalization as a scapegoat for suffering and exploitation. The British created or escalated many of the ethnic rifts in the subcontinent, making issues like exodis from and neocolonialism in Kashmir or the partition more likely and more dramatic.

People that attempt to tally these things lay hundreds of millions of deaths at the feet of the British Raj. Yet such numbers are not well-known!

In fact, the liberal economist Amartya Sen even applied this kind of logic to modern India and suggested that capitalism in India killed around 100 million people from 1947 to 1979. But how often do you hear Westerners talk about the mass death campaign of ongoing capitalism, citing millions every decade? Very few, because this is treated as "normal" and "natural" and not something imposed by the dominant system all around us.

A similar example is looking at the published numbers about deaths in Gaza. What we hear is an outdated number of people confirmed dead. It has almost halted for months. Is this because Israel stopped bombing children, hospitals, schools, refugee camps? No, it is because they explicitly targeted and disruoted the entire system responsible for doing these counts, the healthcare system. But even then, let us say the counts continued. Is this everyone killed by Israel's genocide there? No! These numbers do not include the people dying from poor sanitation (Israel cut off water and electricity), of diseases, of malnutrition, of any kind of malady that could have been treated by the medical system the Israelis destroyed. The numbers of civilians killed by deprivation is usually larger than those directly killed in war. It is rarely reported as the death count of a given war, or in this case genocidal occupation.

So, the greatest missed events are those hidden from us without our knowledge. By controlling the definitions of terms like "killed in war" or "died under colonialism" or "excess deaths". The events hidden by our thought patterns ingrained into us since we were young, taught to us by teachers and books and journalists and entertainment media. They weren't all in on some grand conspiracy, either. At least, not most of them. They were also miseducated in the same way. It is a reflection of the ruling class, filtering down in myriad ways until it dictates our very thoughts.

The Circassian genocide is the example that comes to my mind first. In my experience, most people, at least in Western countries, when they hear "Circassian", they will immediately think I'm actually talking about Cardassians, a race of fictional aliens from Star Trek (or they'll at least remark on how similar these words sound).

I also think the Milan Congress is an event more people should know about. This was a congress on Deaf education in 1880 that declared a ban on sign languages in schools, causing trauma and poverty and general harm to Deaf people for nearly a century until around the time of Stokoe's research on ASL.

Really, the amount of history that people should know is abundant, but a lot of it is also very clearly more important to know if you live in a certain area, right?

I'll prefice this by saying that I'm speaking about people, in Britain, who have a general common knowledge of WW2. There is a group that knows nothing. Even which countries were involved.

I would say that the Munich agreement is known about, but not by name. It's the defining moment of Neville Chamberlain's prime-ministership, He is remembered as a fool and a coward because of it. The man who tried to make a naive deal with evil. If you say "I hold in my hand a piece of paper..." there's a good chance people will know the reference.

Molotov-Ribbentropp isn't well remembered. It's known that the Soviets fought against Germany in the end, but not how things began. I remember learning about the battles of the eastern front in high school history, but if I ever learnt about this pact I never remembered it. Maybe that there was a non-agression agreement which Germany broke leading to Operation Barbarossa, but nothing more.

The Bengal Famine is becoming more well known recently. It comes out when Churchill is discussed. Due to his role as WW2 leader he's held in very high esteem by a lot of people. The Bengal famine is brought up to highlight the man's darker, utilitarian and some would say sociopathic aspects in order to achieve war goals. I think this ignores all the events leading up to the situation though and the wider causes. Those are not discussed.

Hope that gives some perspective.