Mongolian Brutes are the huge Mongol heavies who tower over Jin and shrug off normal hits. They don't flinch and their attacks can't be blocked, so you need the Moon Stance, unlocked after 15 Mongol leader observations or kills, to stagger them.
They rely on raw power. Hammer brutes knock you off your feet if anything lands. Tower shield brutes charge and bash. Axe and halberd brutes have huge reach and spin, and fire lance brutes club you or blast fire at short range.
Swap to Moon Stance. Its kicks and Spinning Strike break through where other stances bounce off. Water Stance also works against the tower shield, and Wind Stance against the polearm variant. Keep rolling away from their big swings, since you can't block them.
The Eagle Tribe fields purple double-bladed spear brutes. They attack fast, most of their moves are unblockable, and they resist the Moon Stance, so there is no single stance answer for them.
Bandits
Bandits are the island's common criminals, attacking villagers, Mongols, ronin and Jin alike. They are a secondary enemy in Izuhara during Act 1, poorly armed and predictable, but reckless enough to hurt you.
Eagle Tribe
The Eagle Tribe is the Mongol force that has taken Iki Island, led by the shaman Ankhsar Khatun, called the Eagle. They are the main enemy of the Iki Island expansion, and their purple-uniformed troops bring units you never see on Tsushima.
Mongol Archers
Mongol Archers are the bowmen at the back of every Mongol group. They are fragile up close but chip away at you from off-screen, so kill them early or close the distance fast.
Mongol Eagle Bearers
Mongol Eagle Bearers are archers or swordsmen paired with a trained eagle that circles overhead and spots you. They fight like normal soldiers, but the bird makes sneaking up on their group much harder.