Well your comment here shows just how overlooked this area of history exactly is.
The most bloodiest resistance in South Asia was offered by states and tribes that now comprise Pakistan.
The British were inflicted around 10,000 in their initial conquests of Punjab and many more as they fought to subjugate rebellious Sardars such as Ahmed Khan Kharral.
Despite Sindh being deeply fragmented during the British invasion, they were still able to rally a respectable defense. Some communities of Sindh, such as Hurs, would continue resisting until the creation of Pakistan.
Pashtuns were able to offer more effective resistance due to the hill/mountainous terrain they presided over, as compared to the plains of Punjab and Sindh which were ideal for the British armies whom were already trained in such environments and hence maintained overwhelmingly superiority in open-field battles. Pashtun guerrillas would continue to fight the British right up till the creation of Pakistan.
The Baloch also offered significant resistance, despite being dispersed and outnumbered, they would offer tough fights at every strategic pass that the British were trying to utilize in order to secure an invasion route to Afghanistan. They had also deployed troops for the assistance of Sindh during the British invasion.
Now compare all that to the 'Battle of Plassey', in which the British were able to conquer Bengal with only the loss of 22 dead (of which only 5 were European).
It would be intriguing to see how history would have turned out, had these powers formed an alliance to combat the British invasion. Though there were some levels of cooperation, such as the Baloch sending reinforcements to Sindh as well as harassing British columns enroute for the invasion of Afghanistan, these measures were simply too little and too late.
A British author explored and mentioned the idea in one of the first British book on the Indus Region written in 1851.