Myrmidon

You have spent time mastering the use of repeated attacks to lower an enemy's guard. Rogues who specialize as Myrmidons are opportunists in combat, excelling in the use of bladed weapons and swift attacks to create openings for a finishing blow. Most Myrmidons carry two weapons in combat, ensuring they have as many opportunities to land that crucial strike as possible.

If The First Hit Doesn't Work...

When selecting this subclass at 3rd level, you are able to find openings for attacking an off-guard opponent while they recover from a previous attack. Whenever you make a melee weapon attack against a creature, whether that attack connects or not, you gain the ability to apply your Sneak Attack to the next melee weapon attack you make against that same creature in the same round of combat, regardless of the normal restrictions on Sneak Attack.

...The Second One Will

At 9th level, you gain the Extra Attack feature, allowing you to attack twice, instead of once, whenever you take the Attack action on your turn.

Whirling Dervish

Beginning at 13th level, you learn to use each strike to wear down your opponent, making each subsequent attack that much more likely to connect, and that much more deadly. Whenever you make a melee weapon attack against a creature, all subsequent melee weapon attacks against the same creature have advantage during the same round of combat. Additionally, if you land 3 melee weapon attacks against the same creature in a single round of combat, the damage of the third attack is maximized, including Sneak Attack damage, if any.

Overwhelming Ambush

At 17th level, you learn to take full advantage of the opportunity whenever your enemies aren't ready. Whenever you are attacking a creature that is surprised, you may make an additional attack against it whenever you take the Attack action.