Winter Soldiers

The Winter Soldiers were an elite group of warriors that were enhanced by a Super Soldier Serum similar to the one that created Captain America and original Winter Soldier.

Background
According to Bucky Barnes, the original Winter Soldier, the Winter Soldiers were an elite group of five assassins under HYDRA who possessed the highest kill count out of all the assets HYDRA possessed even before being enhanced by the Super Soldier Serum. They were injected with the Super Soldier Serum to replicate the Winter Solider himself. Bucky was tasked to train the Winter Soldiers to see if they could overpower him, meaning the experiments were a success. To the delight of HYDRA, it was. However, the Winter Soldiers, except for Bucky, lost control and started a riot, resulting in all of them being put under deep sleep in Cryostasis Chambers.

Abilities
According to Bucky, the Winter Soldiers could speak multiple languages and blend in with any population without being detected and despite being a group of five, they could destabilize an entire country overnight.