Why did they have to keep moving? Couldn't they have just stopped somewhere? So what if you get covered with snow, you've got "the engine" to keep you warm inside the train.
Were they feeding the tail passengers bugs? How would they even have that many bugs to feed that many people daily? Feeding them other passengers would've made more sense.
To gross out westerners
Why even bother having a prison? Why not just kill dissenters and feed them to the tail people?
The script needed conflict.
What was the point of dipping their axes in the fish?
Art. Prime the axe for killing
Why did the super soldier target Yona?
Super solider was a mad dog.
Train barrels through a bunch of solid blocks of ice and doesn't derail or dent the front?
Who was maintaining the tracks? How does the world collapse with buildings falling apart and ships lying on their side, yet the tracks and bridges stayed perfectly usable?
I get that they were trying to make the front seem super nice, but after 17 years in a closed environment, I really wouldn't think that'd be the case. Where are you going to make the cleaning supplies / paint / replacement parts / etc to keep things that pristine.
Gilliam and Wilford were talking on the phone the entire time, yet no one overheard Gilliam in the tail, where everyone was cramped together
Why did that one kid jump into the engine?
he wanted to be one with the machine
If the world is warming up anyways, why wouldn't you just wait a little longer instead of blowing up the train and killing pretty much everyone
Freedom is more important than survival
That polar bear totally ate those survivors.
and had leftovers for weeks
If everything died from the cold, wtf were polar bears eating for the past 17 years?
The point of the polar bear was to show that the big disaster didn't kill everyone and the train was the conductors own private fantasy island/experiment/whatever