Russia and their allies could now dictate any terms they liked to the Ottomans, the Prussians, and the British. By 1849, they had all been defeated in battle or withdrawn from the European continent in defeat.
The victorious powers decided to hold a conference in Krakow over what terms they would offer to their defeated foes. The Krakow Conference made a few decisions. Spain wanted Gibraltar back from Britain, while Greece wanted Thessalia from the Ottoman Empire. These were terms that none of the members of the victorious coalition had a problem with. Both were agreed to quickly. After that agreement was made, disagreements arose. Austria wanted to humiliate Prussia, while Russia was interested in imposing harsh terms on both Britain and the Ottoman Empire. In the end, no new agreements were made, but a second conference was scheduled for January 1850.
This conference was where the terms of the peace were decided. The Kaunas Conference was solely a negotiation between Austria and Russia, as both Greece and Spain were satisfied by the concessions they had received from the Krakow Conference.
Russia wanted to limit Prussia’s punishment to simply paying reparations while annexing vast swathes of the Ottoman Empire and Britain. They wanted to annex all of the Black Sea coast of Anatolia, Wallachia, and Moldavia. They also wanted to give Bulgaria all of Thrace excluding Constantinople, which would be annexed directly. In addition, Greece would annex all of Thessaly, Macedonia, and Epirus. They also proposed giving the rest of Ottoman Europe to Austria.
Their proposed terms for Britain were even worse. They wanted to force Britain to grant independence to Quebec and their Maritime colonies and to give up all claims to the Oregon Country. Russia itself would annex all British lands with a latitude higher than 60 degrees. Additionally, Britain would be forced to terminate all treaties with any Indian state and cede the lands that the British East India Company controlled directly to Russia. To complete the humiliation, Britain would be forced to take responsibility for the war and pay massive reparations.
Austria, for their part, wanted Croatia from the Ottoman Empire, but their main focus was on Prussia. They wanted to utterly dismember Prussia - Austria would annex all of Prussia’s gains from the Partitions of Poland, Pomerania, and East Prussia itself. Prussia’s Rhineland territories would be made into an independent nation, while all of their treaties with every other German state would be annulled. All of Prussian Saxony would be returned to Saxony. To top all of this off, the entire German Confederation would pay tribute to the Austrian Emperor, who was now also to be crowned as Emperor of Germany.
To be clear, both Tsar Nicholas of Russia (as well as his entirely conservative Duma, which had illegally seized power by this point) and Emperor Ferdinand of Austria were being ridiculously unreasonable. Neither of these proposed treaties would’ve ever been accepted by Britain and most of the European powers. There were a few of the states of the German Confederation that didn’t even participate in the war, so that treaty would’ve been refused even if Britain had caved.
At Kaunas, Russia managed to convince Austria that an independent Rhineland was under extreme threat, so France should be allowed to annex it. France occupied that region during the war, so this provision made sense. The Russian diplomats also convinced the Austrians that the creation of a German state would make whoever formed that state the instant enemy of most of the rest of Europe, so that clause was dropped.
In turn, Austria convinced the Russians that Britain would never agree to such extreme terms. They would fight on instead - indeed, they would fight until they had no territory on the British Isles, in their colonies, and no support from the rest of the world. Britain wouldn’t give up any territory that wasn’t lost to them already. Tsar Nicholas agreed to roll back his terms to extreme reparations and the blame for the war, which would destroy Britain’s prestige.
The truthfulness of Austria’s assertion has been hotly debated. The “Sixty Clause” would likely have been accepted, actually, as Britain didn’t see much worth in their far northern American territories. However, it was scrapped because, well, Russia didn’t either. The humiliating terms concerning the rest of Canada and India would almost definitely have been refused, however.
The Austrian diplomats then convinced the Russian ones that the Bulgarians didn’t want Thrace, and it was likely that Greece would ally with Britain very soon after peace was made. The fact that Greece did ally with Britain almost immediately after the war ended suggests that Austria likely had spies in either British or Greek diplomatic channels. Regardless, Tsar Nicholas agreed to get rid of the clauses giving Greece and Bulgaria additional territory.
Tsar Nicholas didn’t want to grant Austria Croatia, either - he saw that as a land that many Slavs lived in, and he held the view that Slavs should be the only rulers of Slavs. He was something of a Pan-Slavist as well, so he wanted Croatia for himself but not immediately, as that would only embolden the new Duma, which he saw as too expansionist. He agreed to not demand northern Anatolia if Austria didn’t demand Croatia, and the Austrian Emperor agreed.
Nicholas then convinced Austria to not annex Prussian territory, which would spare them from additional revolts. Considering that Austria had a high risk of revolt anyway - as the Hungarian War of Independence would prove - this clause was agreed to.
It’s worth noting that the original terms were proposed at the Krakow Conference by diplomats acting on behalf of the Militarist Russian Duma, while the Tsar personally negotiated at Kaunas. The Tsar was far less expansionist than the Duma, which would come back to bite him. The Duma’s terms might very well have prevented most of the conflicts Russia was involved in after the Great European War.
Still, the Duma managed to slip an additional clause in the ultimate Treaty of Trabzon - that Britain could raise no armies and had to halve their military forces for self-defense for five years. In addition to that clause, the Treaty of Trabzon gave Greece Thessalia, it gave Spain Gibraltar, and it gave France the Prussian Rhineland. The UK also had to pay 25% of their taxes to the victorious coalition for five years and was blamed for the war. Prussia paid a lump sum of around 10 million thaler. These were the terms that ended the Great European War.