Sly 3: Honor Among Thieves

-( Story related, cannot be missed )-
While chasing after Dimitri's scuba gear, you'll eventually be taken upon by LeFwee, who will kidnap Penelope (again). After proceeding through the missions out on the sea map, you'll come back and attempt to take care of rescuing the fine maiden once more. With your upgraded cannons, all you really need to do is survive his assault (as you get a job over if you try to get some distance from him to try and strategically aim).

As the mission continues on, you'll eventually be facing LeFwee himself, as Penelope! She takes on defending her turtle love and challenges the "smartest man on the seven seas" to a duel. Through his first round, he will simply try to low attack you. Jump after every hit and he'll start taunting you. This is your chance to strike with a high attack. Knock him off the mast to start the next round. This time, he'll mostly (for me, all the time) attack high, so press down on the control stick to avoid his attacks and then attack low when he taunts you again.

The third and final round will have a mixture of the two. If he holds his sword up high, swing low, and if he has his sword the same length of Penelope's body, swing high. You should be able to ship him out to sea in no time.