PRUSSIA
In 1861, the Tsar emancipated 22 million serfs. This was just the beginning. He wanted to make a series of reforms that would eventually lead to the Russian people having a constitution.
The idea of a liberated Russia and a constitution were anathema to Prussia. The 1776 US Declaration of Independence was an enemy to Prussia. If Russia did the same, Prussia would effectively be facing 2 liberated nations endowed with individual rights to life, liberty and the pursuit of happiness.
This Prussian fear of such liberty is best described in a Hegel quote.
https://russiapedia.rt.com/prominent-russians/the-romanov-dynasty/alexander-ii-liberator/