You can start this mission after completing the mission 7a (Trash the Stash), which is prepared for hero, or mission 7b (Fight Intolerants), designated for villain.
Wait until the main hero is contacted by his allies and listen to the conversation between the characters. You can now head to the bridge that links the northern and southern part of Seattle. It is located in the eastern part of the map, specifically in the south-eastern part of the Pioneer Square district.
Of course, make sure that you are running down the highway and pass by abandoned watchtowers. Once you reach a huge concrete barricade, make sure that Delsin is currently using a power from Neon category. If not (i.e. if Smoke category is selected), drain fluorescence from a nearby neon light (that will automatically switch power category). As you have probably guessed, you need to use Light Speed ability ??(hold Wheel on the pad) to start running vertically and thus be able to reach the very top of the barricade.
Watch a cut-scene, during which Delsin again starts using Smoke power. While crossing the bridge, the main character has to avoid Auto-Turrets. If you have previously fought for control over the city districts, this is nothing new for you. Otherwise, know that you should be very careful, because the Turrets have huge fire power. Their main weakness is that they do not rotate a full 360 degrees. Bypass the first Turret from the right. Depending on your preference, either destroy (press the touchpad when standing on the back side of a Turret), or ignore it and immediately head on.
Jump at the containers located on the left side, thus avoiding fire from another Turret located far south of Delsin's current position. Choose the right pathway through containers and help yourself out with Smoke Dash ability to quickly pass by the small area where the main character would be in range of one of the Turrets. As before, you can approach the Auto-Turrets that you pass along the way and blow them up or focus solely on pressing forward.
Go across the bridge along its right side, thus passing by two more Auto-Turrets (the one deployed at the highest container and that which is on one of lower containers). Stay alert after you get to the narrow passage surrounded by containers. On the left there is the last Auto-Turret - if you want to safely pass by it, you should again use Smoke Dash power.
Move further south, taking an undemanding climb on the way and, in a few moments, getting to the damaged part of the bridge. There are snipers on the remote towers, and if you have some smoke left (unfortunately, you cannot regenerate it here), attack them from a distance. Otherwise immediately bounce off from the wrecked car (it is the only safe way to reach the other part of the bridge) and use Smoke Dash ability as well as floating in order to get to the place where the D.U.P. soldiers are stationed.
Eliminate the enemies and head further south. A group of slightly better armored opponents will soon stand on the main hero's way. At this point it is good to use all the remaining smoke. Only after having that used up, start performing melee attacks (Square). Unfortunately, you must be in constant move during the fight, so as not to get under heavy fire. After eliminating the enemies, jump down on an even bigger "arena", where, after a brief conversation with Augustine, a new boss awaits you - a Department of Unified Protection Agent.
Let us traditionally start with a few words about the boss's attacks, which is because these are quite diversified and they inflict considerable damage, so you really need to make effort to avoid them. One of the main attacks that the elite D.U.P. agent has, is casting massive cement blocks at the main hero, which you can avoid by running or taking appropriately big covers.
Another major attack the boss has is firing auto-targeting missiles that move under the ground and inflict damage upon contact with the main hero. In this case, it is highly advisable to often perform dodges and run around all the time, hoping that an enemy missile will miss Delsin. Otherwise, the main hero may be seriously injured and temporarily dazed, thus getting exposed for further attacks from the boss.
The last attack D.U.P. agent has, is used in the later phase of the duel. The distinguishing feature of it is that the boss temporarily ceases fighting at a distance. Namely, he will try to perform a single melee attack. As with the previously described auto-targeting missiles, the key to keeping Delsin alive is to avoid such charges by dodging and running, as they may inflict serious injuries.
So much for the boss's abilities, now some information on how to deal with him. The first thing you need to do is to switch Smoke power to Neon power by absorbing energy from one of the neon lights in the area. But do not rush into this (that also applies to regenerating the energy bar later in the fight), but first make sure that the boss is not currently in a position from where he could easily interrupt the charging process and weaken Delsin at the same time. By the way, I recommend getting the improvement that shortens energy absorption time, although you can handle even without that.
Theoretically, you can attack the boss with all available ranged attacks (do not try to get near it - melee combat is not an option), but the best result comes from using a combination of Laser Insight and Phosphor Beam. Start by holding L2 button and right after that hold R1 (Phosphor Beam attack needs a moment to charge up). Now try to aim directly at the boss while in slow motion mode (as in the picture above), waiting for the moment when the missile launches.
Using Phosphor Beam power will only prove successful and take away a lot of hit points from the boss, if the energy beam hits directly at him and not at the concrete elements floating around. From now on, keep repeating all the steps as described above and be sure to frequently regenerate power by absorbing energy from neon lamps, because Phosphor Beam attack requires Heavy Ammo. Reducing the D.U.P. agent's health bar to zero will terminate the duel as well as the eighth mission.
Wait until you are transferred to Lantern District in the southern part of the city. The game will give you access to another main quest, called The Fan.