Left 4 Dead 2

Again theres a very simple tecnique to unlock this in about 30 mins give or take, on your own

1) load up an easy realism dark carnival

2) continue playing until you get to the finale

3) leave the game (you must exit to main menu, do not call a vote as this doesnt work - thanks to DSmooove6 for confirming this) and start up a brand new realism lobby (believe it or not this works i was weiry about it myself) and set it to expert part 5
What to have before setting off the finale on part 5:

- nab a scoped rifle, a melee weapon, a pipe bomb for clearing out the horde when the chopper arives and an adrenaline for the run to the chopper

4) play on until you set up the finale, incap the 3 bots on the stage then set off the finale after grabbing the necesities you need: pipe bomb, adrenaline etc, then run up to the jesus rail

for those if you who dont know where this is, it is on the far left hand side of the stands when looking from the stage, by the blocked off entrance (Video below for visual aid), climb up to the top of the stands and sit on the rail, remembering to keep an eye out for infected climbing up beside you.

NOTE: its a good idea that the in the last couple of Special Infected you killed before setting the finale off was a smoker as he will then not spawn once you set it off, because he can sneak up behind you and ruin the achievement for you, if a smoker spawns when you set it off dont panic and try to find him with your scope before he reaches you

5) but anyway back to the achievement, when on the rail the majority of the common infected will glitch and not move (save a couple behind you on the roof tops KEEP AN EYE ON THEM, as if they fall of the roof they will be able to move and climb up to you. and specials (including the tanks) will not spawn after they have killed of the other survivors. But as soon as you get off the rail it will all revert to normal, so Just dont fall off or it untill the chopper arrives as they will glitch back and you'll have to die and restart from the part 5 saferoom

6) when the chopper arives pull out your pipe bomb and launch it across the map, also take an adrenaline shot or pills if you have them and run for the chopper, you should have enough time to reach it even if it arrives at the other side of the map

i managed to get this on my 1st playthrough, but my 3rd attempt at the finale, as the bloody single infected kept attacking me from behind! but i was very suprised that this method worked as it sounded stupid

NOTE: this method will work on other campaigns i just chose dark carnival as it had the most effective glitch spot, i believe there is a table in the hard rains burgar tank finale that has the same effect.

So just remember to always check behind you when on the rail as commons can still move down in the area below you but you should have no trouble killing them as they climb up!

hope this was helpful ;)

This achievement requires there to be a group of people who are skilled, communicative and lucky. If you soldier on and keep trying (despite how frustrating it gets) you will eventually get it.

If you want to glitch however then I have an easy solution which can also be applied to the 'Still Something To Prove' achievement. Simply follow this guide and prepare to bask in the beauty of a 35G achievement:

1) Load up 'Dead Centre' with 2-4 players.
2) Set the difficulty to its easiest setting and turn Realism Mode on.
3) Complete every chapter except the final one.
4) In the Safe Room before you go on to the final mission have all but one person quit to the main menu.
5) Let the remaining player collect nearly all of the gas cans.
6) The remaining player should then set the difficulty to Expert.
7) The players who quit out should then re-join as quickly as possible and put the last gas can(s) in whilst trying to survive against a lot of hard zombies.
8) Once you put the last can in and the cut-scene comes on, the players who quit and re-joined should get the achievement.
9) Re-do this guide so the loan person who stayed behind has a chance of getting it too. Fair is fair.

This is the way I earned this achievement, but it has been a while since then. I do not know whether the developers have implemented an update to rectify this problem as I barely (if ever) play this game any more.

Thankfully, the TA community are posting in the comments section about whether or not the glitch is still working. If you want my advice, keep looking at the comments to see whether you can use it or not.

*PuckJunkieJames and FedderTheGun have posted some interesting advice in the comments section, read that for further help with this achievement.

Very similar glitch to the ones outlined, but I personally found it much easier to do on the Parish campaign.

1. Start realism lobby on easy mode.
2. Play first chapters on easy realism, do not worry about anything, just have fun.
3. When you reach the saferoom for the finale (The Bridge), after the final chapter has loaded up, everyone who needs the achievement must quit to menu. Note, there must be at least one person still in game, two makes life easier.
4. Remaining players send invites to the players who left in prep, and then play most of the finale on easy realism. The players who left should just sit on the invite ready to accept. Take your time through, look after the AIs. Kill (not avoid) the first tank.
5. Coming to the end of the bridge, kill the second tank, and start making your way over to the helicopter.
6. When approaching the landing pad, do a quick check for a 3rd tank, if you see it, kill it. If not, as quickly as possible go to....
7. Call a vote to change difficulty to expert.
8. As soon as 'vote passed' changing difficulty box shows, the players who left immediately accept invites.
9. If all goes to plan. the AIs will have already climbed into the chopper and the end cutscene will be beginning to play (or already playing). The players who entered bash RT to 'enter' the game and the achievement pops without them needed to make a dash for it.

There is a glitch you can do to get this achievement and it's really simple.
(This might be patched soon so don't tell me it doesn't work)
*Note that this must be done with atleast 2 people.

1. Start up a game on easy with realism.

2. Play through the game normally on any campaign until the last chapter. (Dead Center recommended)

3. Get most of the gas cans in the car and keep the last one close by.

4. The player getting the achievement needs to leave the game now.

5. Once the player still in the game kills the second Tank send the other player an invite to the game.

6. Get ready to vote the games difficulty back to expert, change it once the person accepts the invite.

7. Once he comes back put the last gas can in and get your butt in that car before another tank comes!

*All video credit to acidglow.

ALL GLITCHES HAVE BEEN PATCHED. So in order to do this you will have to delete the update and do this solo. You can use the same method by going back to the main menu and reloading the finale, i would suggest hard rain using the jesus table. Make sure you have the auto shotgun pipebomb and adrenalin, doable without the shot but it helps. Now you do have to watch out for a smoker in which the times ive done this he will be on the roof so watch out as he can still get you. This is IF he spawned before you got on the table, if he spawns after you should be good but still keep an eye out.

Once on the table crouch and "lights off", also make sure your back is to the wall. If your screen shakes when the the tank comes, don't freak as ive had him stand in front of me and die. I have also shot and killed him without him doing anything to me. Just make sure you don't move until the boat arrives, now when you hear the boat DO NOT leave the table or else you'll be standing at the dock waiting most likely to be killed. Just wait about 5 seconds then take your shot and make a mad dash to the boat. Best to throw your pipe bomb out the front of the store or any were but towards the boat(obviously).

Below is a video showing you were the jesus table is. He doesn't crouch or turn the light off but its still recommended.

Credit for the video is zehliquid

Easy achievement to do on Hard Rain.
Load up Realism on its easiest setting.
Run through the first 4 safe rooms.
Before you start the finale, have anyone getting the achievement leave to main menu BEFORE opening safe room door.
Open door, run through and kill any normal infected around the burger shack.
Vote to change to Expert.
After vote is passed, invite players back into match.
Kill any bots as they will mess up the glitch.
Turn off your flashlights and get on Jesus table in crouched position.
The host of the game will be the one to throw the switch.
After you throw the switch, jump on Jesus table and wait for boat to arrive. There will be SI so make sure you get your partners' back on the table asap.
When boat arrives, wait a few seconds before throwing your Bile/Pipe Bomb out of the restaurant.
Slap adrenaline on and run for the boat!
Rinse and repeat using someone who got the achievement as a host.
Good Luck!

Credit to Maniac Strike as I used his technique which you can find under "Still Something To Prove". No Cache wipe needed. Done on Xbox One

Edit: 30/07/2018: I double checked today if this works on a second account of mine and unlocked it within an hour. Recorded most of the run on the bridge so I might try and upload it. It is not a very good run had a lot of problems with Special Infected. You may die at any point and you don't have to quit out. You can just keep trying till you succeed. Also if you have any question feel free to message me on either this or Xbox and I'll reply ASAP

26/07/2018: How I got the achievement was to first use the Mutation Gib Fest, which requires The Passing Dlc, to go through The Parish Campaign. I did this all on easy up until the last Safe House to Part 5: Bridge.

Once the game had loaded me into the Safe House I quit and went to Play Realism, Play With Friends, Create Lobby, Create Lobby. I selected Edit Game Setting, The Parish Campaign, Part 5: The Bridge, Expert Difficulty. I personally chose to play as Coach and then hit Start Game.

I grabbed an Automatic Gun, Pipe Bomb, Health Pack and Adrenaline.

As much as I found sticking to the left of the bridge to be helpful I also found sometimes cutting across the middle, or going up ramps, to be necessary to avoid Special Infected. About half way across the bridge, when you can go up the hummer in the middle to go up a ramp or stick left to go under, I used my adrenaline as there was then a truck up ahead on the left that had more.

Originally I was throwing my pipe bomb at the start but found it was a waste and was better saved for when I could see I was about to be swamped. Once I found a path that worked for me, I only had 2 problems left. Random Special Infected getting me or getting to the chopper, my team not being down or close and then a tank entering the chopper. These two things I can't really help with sadly but this achievement, in this way only took me 1 1/2 hours.

Good luck all and I hope this helps. My first solution so any feedback is appreciated

Having done this a few times (for myself and helping others), this is my recommendation as to the most reliable way of doing this (assuming you have The Passing DLC).

The Passing has the best ending for utilizing the glitch, as there is a decently long run to the rescue vehicle to allow people time to load into the game, and it is a pretty short campaign as well. Plus you have the original survivors to help cover you in the finale, and a chance of getting an M-60.

1) Someone who does not need the achievement should host a realism game on easy in The Passing campaign.
2) Once you reach the third section (The Port), have those who want the achievement quit to the main menu. If you are able to find an M-60, try to hang onto it and it's ammo.
3) Send invites to everyone who quit, but they should not accept yet. Everyone who left should be on the invite accept screen, ready to join when instructed. (You will need to be in a XBL party so they can be told when to join.
4) The host and anyone else who stayed in game should collect all 16 gas cans and load them into the generator. Try to keep your health in as good shape as you can, making good use of the readily accessible ammo pile. Your ideal loadout will be pipe bomb (or bile), adrenaline, and an M-60. But anything you can hold on to will probably be helpful.
5) Once the bridge starts to lower, wait for a break in the action, then call a vote to switch to expert and as soon as it passes instruct the people who dropped out to join ASAP.
6) While they are loading, those in the game can run as fast as they can towards the car. Use adrenaline if you have it, or pop some pain pills or whatever you have.
7) Once you get close turn around and start shooting at any zombies, coming across the bridge. This would be a good time to toss your pipe/bile/molotov.
8) Once everyone has loaded in (and hit RT to actually take control of their characters) hop in the car.