After the bossfight, head down the stairs and call over Sheva to the exit door. After the cutscene, call over Sheva to the elevator. Along the walkway snipe the soldiers below. Jump down the ledges and climb the ladder to the next platform. Head up the stairs to the right and pull down the lever to open the door ahead.
Hop over to the next room and kill the soldiers along the platform. Call over Sheva to pull down the lever to open the next door. While waiting for the next door to open, take out the two Reapers that drop down from above. Once the door opens, hop over to the the next room and take out the two Gatling Gun Majini. Collect the two Hangar Keycards they leave behind and head over to the elevator ahead.
After the cutscene, pull down the levers along the platform to shut down the flood lights above. Grab the RPG inside the glass case. Catch Wesker off guard, and shoot him with the RPG. Quickly run over to Wesker and shoot rocket in his hands. Grab hold of Wesker so that Sheva can inject him with the serum.
Get ready for yet another interactive cutscene.
Once you land on the volcano, cut open the wooden crates and collect the ammo/gold. Head up the walkway to begin round two against Wesker. Along the walkway shoot rock formation to the right. After falling from the bridge, turn left and hop across the rocks. Collect the Diamond (Marquise) that's on the floor. Run past the center platform and head over to the large boulder. Press the appropriate buttons that flash on the screen to push over the boulder. As you head back to the central platform, Wesker will try to knock you off the ledge. Take out your machine gun and aim at the orb in Wesker's back. While Wesker's stunned, head up the central platform.
As Sheva makes her way to the central platform she will trip and fall from the ledge. Provide cover fire across the bridge for Sheva to prevent Wesker from attacking her. After landing a few shots on Wesker, he will get mad and start to throw rocks at you. Doge the rocks by quickly pressing the X button
When the initial boss fight begins, run around Wesker and shoot the glowing orange orb on his back. He will then hit the ground forming a tornado attack with his tentacles. After this attack, a glowing orange orb on his chest will be exposed. Shoot the orb to stun Wesker.
Quickly run over to Wesker and press X to grab hold of him. Sheva will then come over and stab the orb in his chest multiple times (Quickly tap A to keep restrain Wesker's). When in the helicopter, finish Wesker off with the RPG by simultaneously pressing L + R triggers when prompted. Congratulations! You just completed Resident Evil 5!
