TEKKEN 6

I beat Nightmare Train with King and Alisa. Took me about 10-12 attempts but the strategy that finally worked was something like this:

1. You need a number of good S and A-ranked items. To acquire these you can either farm this level or another, such as the Heliport where you fight Kazuya. There are a lot more drops at the Heliport and the level is much simpler compared to Nightmare Train. You really need at the minimum a decent health booster, a decent attack booster, a good ice or electrical attack booster, and probably also a good defence booster.
Note: minus15T has also suggested that playing the Roger Jr. stage on Hard is a good item-farming technique which should net 5-10 items per run of at least B rank.

2. Don't forget to equip Alisa's best equipment as well. You need to keep her alive for as long as possible because once she's gone it gets a LOT harder.

3. The gargoyles are a total nuisance as they guard a lot (normally high). High-low mix-up's and spinning attacks that will hit multiple foes are most effective. When I used King I found his Ali Kick -> Middle Smash (d+3+4, 2) to be helpful at short range, and at mid-range his jumping reverse kick (f+4) was excellent as it would often knock enemies down, setting up for a Moonsault. Whichever character you're using, experiment to find the best strategy.

4. If you get cornered by a big mob, all hope is not lost, just keep guarding and time your counter-attack, then try and get out of there into somewhere you have a bit more space.

5. Unblockables are good if they have a decent range and you can judge that range well.

6. Save the gatling gun for Jin. Once he appears, you can basically blast him off the edge with the gatling gun. This is much easier than trying to knock him off hand-to-hand because gargoyles will continue to spawn once Jin arrives.

I beat Nightmare train way easier then any of these solutions and I'll tell you how I did it.

1. You don't really need any S ranking items, only a decent health bar, (can be A ranking or lower) and it doesn't matter who you play as either, (Same goes for Alisa)

2. Next all you need to do is get into a corner of the train and leave your controller idle so that every time the gargoyles attack you, you'll be constantly blocking.

3. Wait till the time reaches 250 seconds left or just to be safe, wait till 150 seconds are left on the clock, (can't remember which of the two it has to be but I'd go with the latter if I were you!

4. Once the timer hits 250 seconds/ 150 seconds, take out the grey gargoyles that have been attacking you for so long.

5. Nextly, if you have followed all the steps up to this point, no more remaining enemy's should respawn and Alisa should start talking, saying something along the lines of, "I am detecting something incoming" then Devil Jin should appear with little work on your part.

6. Finally Devil Jin should appear! Run towards his location and get the Gatling gun, target him and try to shoot him off the train as fast as you can! Done! If you fail and get mauled by the gargoyles, especially the bigger ones you can always try again, remember there's always next time and you don't have to get frustrated knowing that you have to beat loads of gargoyles as per normal without this method.

Hope this helps people out there who are in desperate need of completing the Nightmare Train!

The Nightmare Train level becomes available after beating Story Mode for the first time.

I found that switching characters so that I was controlling Alisa made things a little easier. Her basic B-button kick can hit multiple enemies, is very quick and is quite powerful so just use that. It doesn't really matter who the AI controls, just make sure they are well-equipped.

You may (read: will) have to keep farming the level for item drops so start off with items that raise your health and your drops. Once you've got something to wear in an S or A rank that adds health, equip some ice, stun, attack power and defence increase.

You don't need to nullify any elemental attacks. The gargoyles don't use them.

Try to save the gatling gun for the brown gargoyles. They are total pricks and deserve to be shot in the face.

After a few waves of gargoyles, Devil Jin will turn up. He'll probably have six or so gargoyles with him and he'll finish you off pretty quickly. The way to beat him is to stand in the middle of the level and try to knock him off of the train. Don't worry about his stoney butt-buddies. Just concentrate on getting him off of that train.

I made this with the regular team (Lars and Alisa)

You need to farm some Rank S and A items to do this,remember that they can be acquired more easily on some level at hard difficulty setting.
WARNING: the item's effect DO NOT STACK! so pick up just one for health,defense,attack and any elemental damage (I indicate fire or ice) for both characters.

After that,put difficulty to medium and start nightmare train level.I suggest to don't use the machine gun at first,save it for when Devil Jin appears. Until then stay close to your AI partner and basically do these 3 things:
- Hit a low attack ('cause gargoyles tend to block more high attacks than low attacks) FOR LARS I SUGGEST DOWN + B BUTTON ;
-Block as many times necessary (Yeah,it's a patient test);
-Break crates for itens or pick up from fallen gargoyles.

OBSERVATION: you can hit some high kick attacks to make them fall from the train,but isn't 100% chance to do it.

After the cutscene appears,run where the machine gun is placed,take it,aim on that demon bastard,but not to hit him only,the strategy is to hit and make him fall from the train.
If you make all through here right,then congratulations! Achievement popped.

HERE'S A YOUTUBE VIDEO FOR IT:
(I don't own credits,give them all to sk8pirata)

Though i've read up on a lot of things saying "use the gatling gun to knock Jin off the train," if you find yourself cornered by a million gargoyles after spraying as many bullets at him as possible, you can still beat this stage.

I've been using Hwoarang and Alisa, both with a decent amount of A items (Hwoarang has 80% attack, 8 defense, 300+ health, 70 fire attack, 35 ice attack, Alisa with similar but weaker items) and i still had trouble doing it. But the best way i found was to be ruthless with your onslaught, going for low to mid/high combos wherever possible because of their guarding habits. If Alisa goes down, go on the defense, deliberately back yourself into the corner where the gun is (assuming you haven't destroyed the boxes with the chickens in them yet) and wait for your chance to use a throw. When you throw, all the gargoyles surrounding you will fly about everywhere, giving you a chance to escape, and grab some health, from crates or enemy drops. When this happens, a fair bit of health will deplete from the enemies, sometimes knocking them off the train altogether, or singling out one or 2 gargoyles who'll chase you straight away, leaving you with a good chance to take one of them out. (With the high level fire attack item equipped, even a quick X jab can inflict a lot of damage, but only if you time it right, and preferably if you're one on one with a gargoyle.) You can use this temporary freedom to heal Alisa, who can help taking out the remaining gargoyles. If she falls again, keep defending and throwing. Repeat as necessary until Jin appears.

When he does, use the gatling gun, but if this fails, keep guarding yourself into a corner, defend, and throw. If you're lucky, Jin will either jump off the train while you're guarding (that's what happened to me) or you'll knock him off if you end up throwing a gargoyle. Either way, if you're timing is good with the counter throw, you won't have to worry about a lack of health because you can't really be harmed, unless Jin low attacks you, in which case, you're in trouble.

Much like the solution for the Survival achievement Kazuya is the answer here. I beat the Nightmare train on hard on my 4th try with him with only two upgrades (Life meter and attack). His up+fwd b,b,b,b attack is absolutely effective at keeping the crowds off of you and Alisa, punishing those on the ground and even knocking a few over the railing.

Obviously keep the chain gun for Jin like the others suggest, I knocked him over the edge by accident with it.

Here is me completing the Nightmare Train, basically using m0rph3us17's guide as a reference. Did around a dozen runs of Roger Jr's stage on Hard to get some decent items and then was able to complete on my first run after farming. I had attempted several times before this and failed miserably. I also get really lucky with where Alisa knocks Devil Jin just as I pick up the Gatling Gun.

At the end of the stage I also show the respective loadouts for each of the two characters, didn't realise I'd left Drop Rate on King...