Wesley R. Ball’s review published on Letterboxd:
It's not what you do, it's when and where you do it, and who you do it to or with. If nobody sees it, it didn't happen.
I'm just gonna warn everyone right here: Remember in the trailer at the end where Johnny Depp does that epic clap that perfectly syncs with "Til It's Gone's" tempo? It doesn't happen in the movie at all. That was probably the most epic part of the trailer and they just pulled it right out from under my face. It was a pretty big disappointment for me. The story itself, however, is quite fascinating, although its execution is completely misleading as well.
All of the posters and the trailers seem to indicate that this film is about the rise and fall of James Whitey Bulger and his questionable informant connections with the FBI. However, the film actually puts most of its focus on Agent John Connolly and his own questionably corrupt ethics. Which is a real shame, because his character ended up being terribly uninteresting to me. Johnny Depp leaps out of the screen as Bulger, and he gives the absolute best parts of the film, possibly the performance of a lifetime. But when the film decides to shift its entire focus onto the downfall of this FBI investigator, the character development and story just fall flat.
Bulger is a regular Trevor Philips. He doesn't take anything from anyone and does what he wants, whenever and wherever he wants. Only problem is, there's some territory on the other side of Boston that his gang is at war to control. So what's the easiest way for him to gain control of this territory? Strike up a deal with the FBI as a snitch-but-not-really-a-snitch, of course. Bulger's constant denial towards being an FBI informant provides some great tension between him and his other gang members, and supplemented the perfect "downfall" storyline. It's unfortunate that the director decided to switch the main focus onto the FBI agent's corrupt dealings and Bulger's information feeding instead of the actual rise and fall of the criminal mastermind. It just became so uninteresting that I kept asking myself "Where is Johnny Depp? I came here for Johnny Depp. Not the creepy dude from The Gift." It's just a massive spin on expectations that makes me trust trailers nowadays even less than I already did.
If you're truly interested in FBI and police procedurals, then Black Mass just may be the film for you. Johnny Depp may have some serious Oscar potential in this role, and I won't be surprised if he is nominated. But the way the film chose to utilize its subject character was ultimately so dull and disappointing. If it weren't for Depp's performance of a lifetime, this movie would have completely sunk under the radar. I don't have high hopes for this film's financial success either, given that the Friday night screening I was in was almost as scarce as my Fant4stic one and consisted entirely of people at least 15-20 years my senior. I'd never felt so weird in a theater crowd since I went and saw The Artist, which was basically like sitting in a nursing home for 100 minutes. The trailers for Black Mass look like they try to appeal to younger, cooler moviegoers, but the reality is that the story is too flat and uninteresting for modern audiences, when Bulger is put on the backburner. It was a disappointment to see where the film's focus truly lied, and I had hoped for something more. Still, it's definitely Depp's best performance in years, so at least that's something I walked away with.