This might be an example, but it’s complex enough that it could be debated.
The British Raj had two basic components: (a) territories directly ruled by the Raj, and (b) princely states, which were independent kingdoms under British suzerainty. When the British left India (and gave India and Pakistan independence), British suzerainty over the princely states lapsed, and these kingdoms were free to do whatever they wanted to.
So, India and Pakistan then went and tried to negotiate with each and every one of these kingdoms to join up with one or the other country. And in the vast majority of cases, negotiations were successful and the kingdoms were peacefully annexed by the new countries.
But, there were a few holdouts, and in those cases, either India or Pakistan annexed by force. Obviously, when force is used, atrocities are going to happen, but none of these kingdoms were in any position to defend themselves, so the annexations happened quickly. There was some concern that Hyderabad would be able to put up a fight, but they completely buckled as soon as India invaded.
I’m going to push Kashmir off to the side here for purposes of this discussion, because that’s a weird case that doesn’t follow the story I laid out above. And there were a lot of nasty atrocities committed by all sides in re: to Kashmir, so what I’m saying here doesn’t apply to that particular princely state.
So, leaving aside Kashmir, were these conquests benign? That’s somewhat debatable, but neither country annexed these kingdoms with the goal of subjugating or oppressing the local populations. And from this point on, I’m going to focus on India, since I’m more familiar with its history than Pakistan’s post-independence history.
But in the case of India, the country is so diverse, that it doesn’t really go around purposely destroying local cultures. It could certainly protect local cultures better than it does (or has done), and there are certainly legitimate grievances, but India didn’t go into Hyderabad and start wiping out people or surpress the local languages or anything like that. The people in the annexed kingdoms were given equal Indian citizenship.
Now, post-independence, India undertook a pretty massive property/land reform to break up the tenant farming system and re-design the economy along more centrally managed lines. And during this process, a lot of wealthy people were forced to sell off property for less than it was worth (or could have been worth), and in some cases, the Indian government outright confiscated property. So, India did muck around with property rights in the newly acquired kingdoms. But again, here, the intent wasn’t to be exploitative, but rather to undo what were viewed as opressive economic systems.
So, I’d rate most of the annexations by India of the princely states as relatively benign.
There’s also the annexation of Goa by India. This follows a similar model to the annexation of the princely states. It was annexed to put an end to colonialism on the subcontinent and India viewed Goa as Indian territory. And once the annexation happened, the Goans seemed largely okay with it (unless you want to spend three hours listening to my uncle rant about how Goa should be independent). But the annexation wasn’t undertaken to exploit resources or the local population or anything along those lines.
So, take that for what it’s worth. There are plenty of people in India who have legitimate grievances against the Indian government, so if you don’t want to consider the annexations benign, I’m not going to argue the point (unless there are factual errors that need to be corrected).