Upvote:4
There is wide criticism that president Medvedev in 2010 has gifted wide areas, equal to two Moscow oblasts to Norway.
https://realtribune.ru/news-authority-5056
But you may be would not count it, because the areas were a) marine (e.g., no dry surface), b) contested.
There was also criticism that in 2004 Putin gifted to China the contested islands on Amur river: https://lenta.ru/news/2004/10/20/islands/
https://lenta.ru/articles/2004/10/20/island/
https://sakhalin.info/news/25947
Also, in 1991 Gorbachev gave China about 600 contested islands, including the island Damansky for which there was a border war between the USSR and China in the 1960s. Some of that gifted territory was in Russian Federation, but other in other republics.