That is exactly the kind of assassination to which Attack on Titan submits its characters in the span of a single chapter (Or 45 pages).
Sadly, there isn't a really good cut-off point (Like volume 48 of Bleach or volume 7 of Death Note, etc) unless you don't mind ending your reading in one of the massive cliffhangers. Though none of them pay-off in the long run, so it's a "Pick your poison" kind of deal.
The fact that it goes downhill at the last possible moment only makes it the more infuriating.
This manga will only leave you unfulfilled or in denial at the thought of the massive wasted potential.
