Instructions
Climb the stairs of the shrine at the end of Chapter 25: Broken Paradise. After the cutscene, take out the snipers and soldiers along the path while using the pillars and crates for cover. The snipers and soldiers should not present much of a challenge at this point of the game.
Jump down the platforms at the end of the path until you reach Lazarevic, the final "boss" in the game. Another cutscene commences, and the fight will begin afterwards.
Note your immediate threats in the area. Avoid the center of the area you're standing in, as well as the small chasm that you can fall into and die.
Run away from Lazarevic any time he gets close. For the best results, stay on the opposite side of the arena. As Lazarevic moves, run in the opposite direction to keep your distance and survive the first phase of the battle. The phases are divided by three cutscenes that are relatively short, but pace the fight.
Aim for the resin bulbs as Lazarevic passes by them. The resin bulbs come from the glowing blue Tree of Life. If you shoot a resin bulb when Lazarevic is near it, it will cause significant damage. Take cover (if possible) once you have gained enough distance so you can see where Lazarevic is heading next and aim at the correct bulbs.
Continue avoiding Lazarevic and shooting resin bulbs to bring him to his knees three times during the battle. Lazarevic will throw grenades at you after he has been brought to his knees the first time. He may also shoot you, but keeping your distance will reduce the damage you take and increase your ability to dodge his attacks. After Lazarevic falls to his knees the third time, your attacks begin to cause more damage.
Shoot several more resin bulbs as Lazarevic gets close to them. The game-ending cutscene will play once you've depleted his energy and defeated him.