User blog comment:Jasca Ducato/Assassin's Creed III - My Review (Xbox 360)/@comment-82.73.209.137-20121112144717/@comment-6517-20121113002211

I've managed to do this a few times; you have to press the Y button whilst you are still attacking the first enemy, but have a second highlighted. This will combine the two animations into a single one, as seen in your YouTube link.