Both movies are:

a: Based on true stories.
b: Involve the murder of a woman/women.
c: Involve police trying to catch the killer(s).
d: Occur in rural settings with one on a farm and the other near a village and railway track.

How they differ:

MCOPPR is:

a: Thai.
b: Gang rape and murder.
c: 1970s crime that was eventually solved.

Missing:

a: Korean.
b: Involves a psycho serial killer that has murdered multiple women, I believe, including a much loved sister. He attempts to do the same to the other one when she stumbles across his sadistic path when searching for her missing sibling.
c: Graphic violence shown is quite brutal.

a: both are based around teens and high school ages/family life only the appeal isn't limited to a younger audience.
b: both have first time love and time travel only TW goes back to 1995 specifically and ATCY jumps back to the 80s then forward a few times like the early 2000s and on.
c: both have really different yet good story lines that involve trying to change something in the past to alter the future.
d: both have a bit of a dark side - one involves a serial killer and the other hidden abuse.
e: both series have strong bonds in it whether family or friends.
f: TW revolves around music - ATCU does not.
g: ATCU is about saving two lives that were tragically lost whereas TW is about changing fate if possible
h: Both have some really funny moments.
I: ATCY is the only one with an evil person or two.
j: In TW the parents are deaf and run a small family restaurant whereas in ATCU the main female's parents don't really see passed their son and the main male's parents are typical parents I suppose.

a: both are based around teens and high school ages/family life only the appeal isn't limited to a younger audience.
b: both have first time love.
c: both have good stories only RB is more on the wholesome side and all about life lessons in one way or another.
d: both have a bit of a dark side. Eg Hidden abuse.
e: both series have strong bonds in it whether family or friends.
f: RB focuses on a sport whereas TW is about music.
g: both have bromance.
h: RB doesn't have time travel.
I: the main lead in RB is also one of the main leads in TW.
j: In TW the parents are deaf and run a small family restaurant whereas in RB both parents are coaches.
k: both have really funny moments.

It is a fantastic Korean movie to watch from start to end.

Monstrum is like All of Us Are Dead in that a monster manifests out of nowhere, only in a rural area, and kills indiscriminately like no tomorrow. Also, it devours it's human prey and leaves mutilated body parts all over the place and fair share of gore in its wake which is not too dissimilar to the not so smart zombies.

Something else they have in common is the battle for survival and a group of people having to deal with it that are directly impacted by it.

One difference is All Of Us Are Dead is based in modern times whereas Monstrum isn't, also, one is a tv series and the other other one isn't.

NOTE: I was here to recommend Duty After School and Sweet Home, but seems I am left with Monstrum.

I would recommend all three.