I'm from the UK so this is going to be a long list, buckle up
The desecration of religious rights in India in the 19th century but executing people via tying them to the end of a cannon and blowing them up
The use of concentration camps in South Africa in the 1890s
The extermination of first nation people in Canada
The extermination of aboriginal people in Australia
The continuation of slavery in areas run by the East India Company
The use of Agent Orange in Malaysia during the Malayan Emergency (1948 - 1960)
The torture of Malayan POWs
The Batang Kali massacre
War crimes in Malaysia
Basically everything we did in Malaysia
The forced starvation of 1 million Irish people during the Potato famine
The role we played in the Bengal Famine of 1943 which killed between 2.1 million to 3.8 million people
The rape and torture of POWs and civilians in WWII
The bombing of Dresden (Germany)
This is only a small list of the various 'we don't talk about these things' things that we have done in our history.