What is commendable

-- The first half makes the audience feel sympathetic, while the second half keeps you on the toe ... 

-- Although seemingly a plain narrative, as it progresses to the end, you wonder whether it is a philosophical film ... about so many issues ... 
... individual/collective
... sense/senseless
... presence/absence
... possession/lost
... survival/life/death
... and even religion
etc

What could be better ... 

-- I presume all have a part to play (i.e., the actor, the director, the editor) ... although the initial plot (in the younger days) do make us empathize with the main protagonist's plight, his older days and subsequent "murder rampage" was far from sympathetic ... the second half , in its pursuit of a thriller, lack characterization and convincing transformation to make the audience side with the main protagonist ...

Conclusion
Recommended ... for being able to "sustain" an audience's interest despite its 2.5 hrs film (the second half seems like a thriller) ...