Mysore under the Haidar Ali dynasty (1761-1799) was one of British India's most implacable foes in the 18th century, fighting the East India Company to a stalemate as late as the 1780s through its innovative technological and administrative reforms (the Mysorean rockets, for instance, or its degree of centralization nearly unprecedented in India). But in the end, the kingdom paid for its resistance. Partially dismembered following the Third Anglo-Mysore War in 1792, it came to a short but bloody end in 1799, when its capital Seringapatnam was captured and sacked and its ruler, Tipu Sultan, killed. The story inspired quite a few Orientalist painters, such as Henry Singleton's ""The Last Effort and Fall of Tippoo Sultaun":
However, Seringapatnam's fall in 1799 was just as much luck as skill. The British had been attacking for more than three weeks, and when the city fell the besiegers had only three days' worth of supplies remaining. If Tipu Sultan had held out for just three more days, the British would have been forced to retreat. To be sure, by May 1799 the Mysorean army had been broken. But on the other hand, the Madras Presidency and many EIC directors thought of this Mysore war as a waste of money and resources - so it is not inconceivable that the British would not have allowed Tipu Sultan to survive in a larger rump Mysore than IOTL (compare
Mysore in 1784 with
Mysore in 1860), albeit with reduced power and as a subjugated monarch.
But the bigger ripple effect is on the Anglo-Maratha Wars. The easiness of Tipu Sultan's defeat convinced the British to take a more hard-line stance against the Marathas, directly contributing to the Second Anglo-Maratha War which conclusively ensured British hegemony across the Indian subcontinent. With a less conclusive and more drawn-out Fourth Anglo-Mysore War, Maratha power might well survive for longer. And that, of course, has its effects on the emerging Sikh kingdom, or on any confrontation between the English and the Burmese.