You'll begin by taking out three anti-aircraft guns. These are not terribly difficult (compared to some of what you've been dealing with recently). The big problems are the drones hitting you with grenades while you're trying to take out the First Sons surrounding each gun. Use Shockwave to deflect the grenades and stun the drones enough to get a clear shot. When the drones are gone, you can turn your attention to the mobs on the roof. You should, of course, be on a different roof. Take your time and ignore John's pleas for you to get in gear.
Take each gun out with a Lightning Storm and move on to the next one. When the third gun is toast, move to the roof marked on your map. Then, it's time for another chase across the city. Stick to the wires; if you fall, you fail. You can't let the chopper and truck get too far ahead of you. You will probably take the wrong path a couple of times, but it's okay, just start back at the last checkpoint and pick a different wire. For the most part, higher is better – you can always use Static Thrusters to move ahead if you have plenty of room to glide.
When you reach the pier, it's time to pull out Lightning Storm. Yes, you can cautiously advance through the maze of shipping containers and use Grenades and Hammers and Precision to pick off the First Sons, but really, you're going to be overwhelmed (and more than once), especially by the drones constantly buzzing up to you and pelting you with grenades. There are plenty of energy sources on the pier, so when you see a group of red dots ahead of you, step out where they can see you and unleash the Storm. Then, duck back behind a crate and recharge and do it again to the next mass.
When you reach the ray sphere, you are presented with a Karma Moment. The Good path is to destroy the sphere. The Evil path is to activate the sphere to enhance your Powers. This is a very important choice and you are well advised to pick the option that correlates to the way you have been playing up to this point – especially if you've been playing Hero.