This is Professor Aldrete's criteria for what constitutes a decisive battle.
My current submission is the Battle of Chinkiang, purportedly the last battle of the First Opium War. This strategic victory for the British brought to China a century of foreign, colonial domination - and I believe the argument could be made that 20th century Chinese nationalism, anti-foreign sentiment, even the Chinese civil war and the victory of Mao Tse Tung can be traced back to roots in the Opium War.
My list tends to favor battles that curbed or ended the growth of various expansionist empires because without such key defeats, those empires might well have extended their political and cultural domination yet further.
What about battles that have the opposite affect? What about Battles which were a turning point where an expansionist empire expanded dramatically after a victory?
I would provide as an example the frontier Battle of Fallen Timbers, where General Mad Anthony Wayne defeated the last successful Native American Coalition to stand against the United States Government (and the British Colonial government prior to that).
in the late 18th Native American Coalitions centered in the Ohio Valley and Great Lakes region had blocked American expansionism at the Appalachian Mountains. Trickles of settlers emigrated into the vast American interior but most were thwarted by these Native American Coalitions of Shawnee, Miami, Wyandote, Mingo, Ottawa, Delaware, etc,.
After the American Revolutionary War ended and our new Constitutional Government was in place President Washington put his focus on the settlement of the vast American interior. His first attempt to displace the Native Americans, so that settlers could enter the interior, ended in catastrophe with the first battle ever by the US Army ending in a defeat known as St. Clair's Massacre at the headwaters of the Wabash river (at present day Ft. Recovery, OH).
Washington's next attempt proved spectacularly successful as he chose the right man for the job in Gen. Mad Anthony Wayne. Wayne properly trained and supplied a small army that routed the Native American coalition that culminated in the battle of Fallen Timbers near current day Toledo, OH.
After Fallen Timbers the Native Americans who had waged war against American encursions, fairly successfully for nearly 200 hundred years were spent as a military force and what had been a trickle of settlers into the interior held back by this Native American coalition became a flood and within two generations the entire interior of the United States had become settled.
So though Fallen Timbers was a small frontier battle in which there was a small number of combatants the long term consequences were profound. It was an unmitigated catastrophe for Native Americans for whom to this day they have never recovered and it opened an entire continent open to settlement by European settlers that was a turning point for America becoming the great continental empire that it is today.