Spain was probably the biggest loser, with the Iberian peninsula ravaged by years of fighting it was impoverished for years to come and the scene was set for being unable to keep its south american colonies in the coming years.
At least France bounced back relatively quickly and was soon a great power again. Without much fighting on home turf while the butchers bill in losses was high, it was not mauled domestically like Spain was and before long was back at the top table, albeit never top dog again.
Russia no doubt gained prestige, some territory in Poland, Finland and Bessarabia, but still on the fringe of Europe.
Prussia had the stage set for the push towards domination of Germany, but it still look 55 years to complete and only after a further series of wars. Victory in 1815 was just a milestone on the road really. But compared to the defeats of 1806 and the low points thereafter 1815 was certainly marked a surge in national confidence.
Austria-Hungary survived. That is all.
USA suffered a loss of prestige in proving to be unable to defend herself at sea or land, despite what revisionist propaganda might suggest, however the Louisiana purchase (firesale) from a cash strapped Napoleon who feared he would lose it anyway, was the deal of the century (or all-time probably) and set them up for a century of expansion.
For Britain of course gained the most, from hamstringing 2 major colonial rivals and gaining a few more colonies, gaining complete control of the sea, and more of less maintaining the status quo on the continent, stretching the national debt but without breaking the bank, and without too much bloodshed relative to the continentals its hard to see too much downside to the result in the grand scheme of things.