This page of our guide to Doom Eternal contains a detailed walkthrough of the Final Sin mission.
Our campaign walkthrough only shows you how to complete the mission. Information about the secrets and collectibles are in a separate chapter of our guide.
Reach the Icon of Sin
You return to Earth to stop the Icon of Sin. Jump on the wall next door and climb up - prepare for a huge battle. There will be many variations of demons - use your strongest weapons and defend yourself against enemy attacks.
After it is over, go upstairs and jump into the ruined building. From here, you have to jump on the successive walls up to reach the next ruined building.
Get inside and kill more demons. Shoot the button to slightly lower the elevator. Now climb into the shaft, jump on the wall and climb higher. There is a lot of demons waiting upstairs, don't let them stop you and run up the stairs. Icon of Sin isn't far away!
Climb the wall above and face a horde of enemies at the top of the building. Then use the bars to jump to the next building and kill even more demons. Climb the walls and run up the stairs to the next enemies.
A giant wave of the most powerful demons awaits upstairs. After beating them, jump through a hole in the building and grab the wall.
Complete the platforming sequence and you will finally get to the game's final boss - Icon of Sin. The boss fight is described in a separate chapter.