You'll appear on solid land after the last mission and some DUP forces will come to attack you. Take them all out and then Delsin will use the phone app to try and track Hank down. Climb onto a high building and press Up on the D-Pad to get a position on him. Get close enough and a marker will appear on your map, where there won't be anything but some ruins of a battle.
However, some DUP forces will show up to ambush you and it's up to you to defeat them. Once they're finished or enough time passed, you will have to locate the signal again, so get onto a high building and use your phone to track Hank's position. The next spot you have to investigate will be on top of a roof, where there will be more DUP and likely a chopper as well.
Track him one more time and you'll see that Hank is heading to the marina, with a marker appearing on your map. When you get there, you'll find him standing there and all you have to do is hit him to initiate a cutscene. You'll be presented with one final Karmic choice, either to spare Hank (Good Karma) or to kill him (Evil Karma). Whichever you choose, the mission will be over.
