Just got back from the cinema, and I really enjoyed it. Some real gruesome stuff near the end....but not as effective as the carnage in Rambo (2008)
But....
As others have remarked, it doesn't feel like a 'Rambo' movie (and I don't just mean the tonal or geographic shift, either) Stallone (for all intents and purposes) plays it like an R-Rated 'Rocky' movie (in terms of character, dialogue and demeanour) Rambo is (usually) monosymbolic in these movies (likely due to being either shell-shocked from his war experiences, uneducated or just plain unfriendly) But here, his speech pattern (and delivery) are just too upbeat and wordy in the first half (and it's hard to believe that his medication for PTSD would alter him that drastically?)
Secondly, when Rambo first went to Mexico....he exhibited no-signs of the 'Tactical-Stealth-Like-Reconnaissance-Expert' traits, that the previous four movies had established. And despite being clearly outnumbered on the rooftop (by around 30-1) he made zero effort in defending himself once the fists started raining down (to be fair, this is probably a more realistic scenario....but very out-of-character for a 'Rambo' movie?) It set the scene for the revenge that was to follow, but seemed odd that he just handed himself on a plate like that in the first place?
As I said, as an actual standalone movie, it was great, and none of the aforementioned 'problems' I had with the character, would even exist, if this wasn't a Rambo movie. But as it stands, 'Last Blood' is a worthy 'Stallone' flick.....but a totally misplaced entry in the Rambo franchise.