I'm not worried or anything. My
Anglo-French timeline has a lot of it, e.g. search for the Oswald Perrin story, or search for the word genocide. I'm genuinely curious how other TL writers handle this topic when writing about colonialism, totalitarian states, total wars, etc.
I leave in existing Genocides unless there is a clear reason the genocide is avoided. As to new areas where there is potential genocide, I look for similar circumstances and tend to make sure it falls in the range of OTL outcomes. So for colonialism, I don't put in genocide in the sense of planning. Colonial killing tend to be out of not caring, so you might well get deaths due a famine cause by not planting the crops due to X. Or disease Y spreads faster due to poor sanitation in refugees camps.
IMO, genocide tone should be similar to the rest of the ATL. So say you have an ATL with massive bombing of cities. Did you just focus on lost production in the ATL? If so, then you probably should not mention the genocide unless it impacts war supplies. On the other end of the spectrum, if you put a significant character and showed the suffering from nation X bombing campaign, then you should have a similar character in the genocide area.
Also, you just can't write a major ATL involving a war and not have some war crimes. Wars always have war crimes.
So to get to specific and it has been a few years since I wrote an ATL. I increased the death toll in Serbia from 25% to 50% of the population due to the Bulgarians cutting off the retreat route. Probably one post on this topic. I spent a lot of time on the "soft" Austrian ethnic cleansing in Poland, but this was required because a Austrian dominated Poland is so much different that OTL or even most ATL where Germany wins. To colonialism, I did not spend a lot of time on the African atrocities. I tried to do the commentary here by illustrating a black officer rising to the rank of Major General and commanding multiple corp. And illustrating how his troops became mostly blacks due mostly to non-combat deaths. I sort of assumed the reader would understand that if the armies are taking over 25% annual death rate to disease, the civilians are dying faster.
I started a rewrite that I probably will never finish. Here I was working more on my story telling. I planned to use the slums of Douala to illustrate the issues of suffering. Got a bit into polygamy with some of the characters, sort of assumed you could figure out why there is a surplus of women. i.e. excess male deaths. Also focused a bit on certain tribes rising, and think this implies other are falling. If I would have gotten to the war years, I would have had either the German Army in Nigeria or the German Army in the Congo go a bit rouge. i.e. Classic slaughter of males, old, children. I put in place a Boer character so I could have the option of having a Black officer or a white officer lead the crimes. I vaguely planned a bit of conflict here, but never thought through it much. Probably something like the Boer wanting cheap labor and being appalled at the wasting of prime working age black males and the black leader doing more classical type rape/rob/pillage.
Now the issue is that I can't give you the better details of writing due to skills, but IMO, a genocide should be obvious enough that the reader knows it happens but not belabored, unless your ATL is about genocide. A reader should not have to think hard to know if one army is trying to follow the rules of the day and the other is not.