Act 5 is the shortest of the acts in Gears of War. It consists of the Special Delivery, Train Wreck and Pale Horse.
When you first arrive at Special Delivery you want to focus your fire on the Snipers on the walkways above. There are two to start of with on the centre walkway and another spawns in the left corner close to where you start as the battle progresses. The objective here is to simply take out all the enemies until the train passes. An emergence hole opens at the far left side which spits out wretches and once you clear it, another one opens at the opposite side of the courtyard. The stationary train is also full of drones and grenadiers but you don't have to kill them. After a while the train will arrive, signified by its horn. This dislodges a crate which lets you onto the platform. Immediately run for the platform to trigger a cutscene.
When you come to your senses onboard the train, start pushing up the carriages watching out for Torque Bow wielding Theron guards. From this point on you want to be gathering as much torque bow as you can and relying solely on your other weapons. Once you reach the door, pressing the switch triggers a cutscene in which a Berserker jumps onto the back of the train. You will have to deal with her. There are three ways you can eliminate her.
1) Rush to the end of the train, get her to charge you and then dive out of the way so she goes shooting off the back
2) Rush to the carriage with the release switch, get her to charge you and then dive out of the way, press the switch and watch her float into the distance
3) Get her to charge onto the carriage with the large fuel canister and making sure you are further up the train, toss a grenade at the fuel canister sending her flying into outer space
Once she is no longer a threat, move up the train and follow the prompts that tell you to climb onto one of the chaingun turrets. Take out all attacking Reavers before advancing. At some point a new threat will emerge, Lambent wretches are swarming the train and are trying to bring it down. You have a time limit which is fairly constrictive but it does allow you time to use cover and advance with some caution. All you have to do is step off the carriage that is being dragged down and the timer instantly ends so when you get close, go for a quick sprint and all the enemies behind you will go crashing into oblivion. After all but the last carriage is clear, its time to reload and get ready for the final confrontation.
This is actually a very easy fight if you know what you are doing. Some people would have you fire a torque bow and then switch to longshot and get a headshot on Raam's exposed head but there is a far more simple method. Equip the torque bow and don't stop firing until he is a puddle on the floor of the train. Don't bother with headshots as there is a chance you will miss and if you have been gathering ammo throughout the mission you should have enough. Make sure you stay at your starting point to put maximum distance between you and him.If you have to move, make sure you stay in the light because Kryll are patrolling.
Well done, you've completed the game and netted yourself an achievement.