No one will be ready for what unfolds.

Rating: 9/10 (26 April 2018)

---- WARNING: VERY LIGHT GENERAL INFORMATION ----
I do not believe I have spoiled anything.
Though read with caution or not at all if you have not seen this film. As I detail general feelings aimed toward certain parts of the film.
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Surpassed all expectation; leaves you in mourning after the passing of beloved heroes; waiting patiently to see the events of Avengers 4.
This is quite simply not like anything you have ever experienced in the cinema. With undertones based on overpopulation crisis, genocide, loss and love; nothing can prepare you for the journey this will take you on. This is a movie that subverts expectation of any generic movie tropes you've come to expect from the genre; any issues can be understood and/or explained and Avengers 4 is almost impossible to predict following the events of Infinity war.
The most notable feeling from the film is the complete harrowing silence and loneliness felt in the final 20 minutes of the film; 18 films of backstory have led to this moment; making it all the more heartwrenching to experience.
I have read reviews calling out the following points:

Lack of character development

We live in a world where the 18 other movies exist. This is part of a larger story arc and must be reviewed and objectively appreciated as such; you wouldn't say a book lacks an explanation of the prior 18 in a series. This is a common critic problem, watch the previous films; it is common sense.

The black order lack of development

I don't personally feel over character development makes sense in this film with regard to the Avengers and the black order. Subtle developments are seen throughout, this is a journey built around chaos. The lack of understanding of the group and quickness of events occurring is exactly what is needed. The characters in the story are outwitted, outsmarted and caught completely off guard by the events of the film.
The lack of development is a bonus, it is a realistic representation of what happens in life. Make no mistake, this is a Thanos story; to review it as something less than what it has earned because it subverts and doesn't match the expectation of the audience theories or ideas is senseless, idiotic, unfair and shows a distinct lack of understanding of the bigger picture.

The film moves around too much

I can say 100% after seeing this, the scenes were clear, present and relevant; nothing is vague or hard to grasp or follow. If you are watching the film, there should be no issues; the pacing is brilliant, bringing a larger than expected amount of slow and personal points where you would expect giant set pieces.
All in all, this is a near perfect film. With any issues being trivial or meaningless and understandable given the scale and ambition of the film.
Are things missing? Yes.
Is it understandable why - given the larger picture - these were replaced by more important story points? yes, it is.
Would you like the longer cut of the film? Yes I would, though I understand there is a large amount of deleted scenes that did not take precedent for the 2 hours and 49 minute mandate.
To comment on a few other things. The transitions and scene composition in this film was flawless, melding together exactly the right tone for each scene; this was helped by Alan Sylvestri's brilliant score.
The CGI - bar one 2 second scene - was believable and didn't take away from the film; were the story to be lacking in this department, or the characters not believable; this may have been distracting.
Well done to Marvel and the Russo brothers.
This film stands apart not only from the comic book genre, but films in general as something special, bewildering, exhausting, tense, sorrowful but light-hearted at the right points.
Consider the bar for comic book films raised.

This IS the best comic book film. Period.
Watch it without the backstory of the universe and it falls apart, but let us be realistic; they exist, let us stop ignoring the universe when everything special about this relies on the hard work that has gone into moulding the telling the previous stories.