Head back to The Bunker for a scene and a final decision on how to end all this mayhem...taking down Damien and ctOS.
Damien has control over ctOS, meaning you will have to contend with the Blockers, Traffic Lights, Steam Pipes, and more. Your objective is to reach the Bower Tower and take down ctOS, but when you get there it the access point's firewall is too strong. Kenney suggests you take down the entire network, but in order to do that you'll need to access three junction boxes across Chicago to upload a virus that will give you access.
Note: Not only will you need to contend with Damien hacking the city to try and stop you, but the cops will also try and track you. Be prepared to use all your Blackouts, Jam Comms, and other tools in an attempt to survive long enough to reach all three locations. You should also think about getting a motorbike or boat to help you avoid the police, making this mission much easier.
Due to the random nature of this mission and how it has you racing across the city in whatever manner you see fit, strategic advice is pretty hard to come by.
The best advice I can give is that you keep moving toward your objective, which you should always set a waypoint to so that Damien's scrambler doesn't mess you up, and to use all your skills that you have obtained throughout the game.
If you are close to the next junction box it is worth using Jam Comms, but if you are a decent distance away you might as well let them spot you so you can lose them before the next box. The cops are persistant, but if you use Blackout they will lose track of you pretty quickly. Using these tactics your should be able to get away from the cops and access all three junction boxes, but don't be surprised if you die a few times.
Once all three of the junction boxes have had the virus uploaded to them, and you have escaped the police, you'll need to return to Bower Tower. DedSec offers one last plea, but after everything Aiden's been through it's no surprise he blows them off. Hack into the final access point and shut ctOS down.
While the city reboots in total darkness we can finally track down and finish Damien off. Check your map to find Damien's location at the Windy City Lighthouse and grab a boat to ride out there.
The Lighthouse has no defenses, so make your way to the top of the lighthouse for a scene with some QTE's and complete the mission.
Complete Act 5.