Char's Reworks (Assassin)

it's a rework of assassin.

All feedback is much appreciated.

Bonus Proficiencies

When you choose this archetype at 3rd level, you gain proficiency in Stealth skill and the Poisoner's kit if you don't already have it. Your proficiency bonus is doubled for any ability check you make that uses either of those proficiencies.

Assassinate

Starting at 3rd level, you are at your deadliest when you get the drop on your enemies. You have advantage on attack rolls against any creature that hasn't taken a turn in the combat yet. In addition, any hit you score against a creature that is surprised is a critical hit.

Infiltration Expertise

Starting at 9th level, You become a master of remaining unseen. You can try to hide when you are lightly obscured from the creature from which you are hiding, and have advantage on stealth checks

Impostor

At 13th level, you gain the ability to unerringly mimic another person, You have an advantage on Charisma (Deception) and Charisma (Performance) checks when trying to pass yourself off as a different person.

You can mimic the speech of another person or the sounds made by other creatures. You must have heard the person speaking, or heard the creature make the sound, for at least 1 minute. A successful Wisdom (Insight) check contested by your Charisma (Deception) check allows a listener to determine that the effect is faked.

Additionally you can cast the Disguise self spell at will.

Death Strike

Starting at 17th level, you become a master of instant death. When you attack and hit a creature that is surprised, it must make a Constitution saving throw (DC 8 + your Dexterity modifier + your proficiency bonus). On a failed save, double the damage of your attack against the creature.