Head to the bridge that is marked, which you might have come across before, and use your Neon powers to climb to the top. Delsin will take out the enemies on his own, but it's up to you to actually cross the bridge. Note there will be plenty of auto-turrets on the bridge, so you will want to use a lot of cover to get behind them and take them out.
When you get past the turrets, you'll come to a large gap with two snipers in towers on the other side. Quickly use the car as a launching pad to get across, then blast the two towers. There will be some more DUP guys who can erect shields past the towers and you can hop over the side of the bridge if you need some breathing room.
Drop down into the large, open area and you'll be thrown into a boss fight with large DUP Agent. At first, you want to drain any of the neon spots since you likely have no smoke power left. The boss will surround himself with large rocks and can throw them at you. Shooting his body will deplete his health, but if you can aim the Phosphor Beams, they will drop the boss to the ground.
Doing enough damage or hitting with a Phosphor Beam will put the boss to the ground, where it will come after you. Here, it will use a whip-like attack or try a melee one, so quickly dodge. Since there are many different neon sources to absorb, you can stick to Phosphor Beams for attack, which can take a good chunk of his life. Once you defeat him, some cutscenes will occur and you'll be in the Lantern District.
