Magma
The 64-bit block cipher in the Russian standard GOST R 34.12-2015, with a 256-bit key.
Magma works on 64-bit blocks, takes a 256-bit key and runs 32 rounds in a Feistel-like structure. It replaced the older GOST 28147-89 as the national standard and kept its small block size.
The small block is the main weakness. With 64-bit blocks, collisions become likely after a few billion blocks, so large volumes of data call for rekeying or a bigger block. For bulk encryption, the sibling Kuznyechik, with 128-bit blocks, is the one to consider.