Ambusher. In the first round of a combat, the bandit captain has advantage on attack rolls against any creature it surprised. 

Charger.  When the bandit captain uses its action to Dash, it can use a bonus action to make one melee weapon attack or to shove a creature. If the bandit captain moves at least 10 feet in a straight line immediately before taking this bonus action, it either gains a +5 bonus to the attack's damage roll (if it chooses to make a melee attack and hit) or pushes the target up to 10 feet away from the captain (if it chooses to shove and succeeds).

Mage Slayer. The bandit captain has practiced techniques useful in melee combat against spellcasters.  When a creature within 5 feet of the captain casts a spell, it can use its reaction to make a melee weapon attack against that creature. When the captain damages a creature that is concentrating on a spell, that creature has disadvantage on the saving throw it makes to maintain its concentration. The bandit captain has advantage on saving throws against spells cast by creatures within 5 feet of it.

Martial Advantage. Once per turn, the bandit captain can deal an extra 7 (2d6) damage to a creature it hits with a weapon attack if that creature is within 5 feet of an ally of the bandit captain that isn't incapacitated.

Pack Tactics. The Bandit Captain has advantage on an attack roll against a creature if at least one of the captain's allies is within 5 feet of the creature and the ally isn't incapacitated.

Sentinel. When the bandit captain hits a creature with an opportunity attack, the creature's speed becomes 0 for the rest of the turn.  Creatures provoke opportunity attacks from the captain even if they take the Disengage action before leaving its reach. When a creature within 5 feet of the bandit captain makes an attack against a target other than the captain (and that target doesn't have this feat), the captain can use its reaction to make a melee weapon attack against the attacking creature. 

Multiattack. The captain makes two melee attacks: two with its scimitar. Or the captain makes two ranged attacks with its daggers. Or one attack with its scimitar and one ranged attack with its daggers.  

Scimitar. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 4) slashing damage.

Dagger. Melee or Ranged Weapon Attack: +5 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 5 (1d4 + 3) piercing damage. 

Parry. The captain adds 2 to its AC against one melee attack that would hit it. To do so, the captain must see the attacker and be wielding a melee weapon.