Beautiful Headhuntress

Assassinate. During its first turn, the assassin has advantage on attack rolls against any creature that hasn't taken a turn. Any hit the assassin scores against a surprised creature is a critical hit.

Evasion. If the assassin is subjected to an effect that allows it to make a Dexterity saving throw to take only half damage, the assassin instead takes no damage if it succeeds on the saving throw, and only half damage if it fails.

Sneak Attack. Once per turn, the assassin deals an extra 14 (4d6) damage when it hits a target with a weapon attack and has advantage on the attack roll, or when the target is within 5 feet of an ally of the assassin that isn't incapacitated and the assassin doesn't have disadvantage on the attack roll.

Enchanting Beauty. Male creatures have disadvantage on attack rolls against this creature. 

Multiattack. The assassin makes two Katana attacks.

Dire Katana. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 3) slashing damage. On a critical strike, the Execution reaction effect triggers. 
This weapon is dropped upon defeat as a Vorpal Longsword.

Cunning Action. The assassin can Disengage, Dash or Hide as a Bonus Action. 

Uncanny Dodge. As a reaction to damage that the assassin can see, it halves the damage. 

Execution. When you attack a creature that has at least one head with this weapon and roll a 19-20 on the attack roll, you cut off one of the creature's heads. The creature dies if it can't survive without the lost head. A creature is immune to this effect if it is immune to slashing damage, doesn't have or need a head, has legendary actions, or the GM decides that the creature is too big for its head to be cut off with this weapon. Such a creature instead takes an extra 6d8 slashing damage from the hit.