Superhero movies are all the rage, and X-Men was a major factor in making that happen. But that's not to say the franchise has been utterly consistent to the letter, or even remotely so. In fact, some installments of the larger Mutant universe (pre-MCU, which will ostensibly happen sooner than later) are fine for those whose ages are in the single digits.
Others, however, are not. Typically, these are solo ventures that intentionally push the boundaries of what the core franchise has been allowed to do, but even the core X-Men films sometimes have their moments that might make parents sweat.
The two Deadpool films are obviously the least child-friendly corner of the X-Men universe, which raises the legitimate question of how he'll fit into the MCU. Both films are a hard R, but the sequel makes the effort to go further than the original, e.g. having one of Deadpool's teammates parachute down straight into a wood chipper.
The good news is, Deadpool 2 has a PG-13 version called Once Upon A Deadpool. The bad news is that it's a weaker variation of the so-so original.
Deadpool was a substantial gamble for 20th Century Studios (then 20th Century Fox). The X-Men franchise had always been one of their cash cows, but it wasn't to the same extent of Raimi's Spider-Man trilogy. The subsequent reboots of both franchises petered out with a whimper.
So an R-rated solo venture for the Merc with the Mouth could have been a niche item, and the budget was kept low (which changed with Deadpool 2). However, the film subsequently soared at the box office, but it still has just about everything in it that parents are expecting when they suggest a different, more appropriate film.
Logan is and will remain one of the most well-crafted and compelling films in the X-Men universe, but it's also the most viscerally violent. There's also a (mutant) child almost consistently put in harm's way, and a particularly brutal slaying of not only Professor X but an innocent family, as well.
Logan is a poignant film about putting one's own life on the line for another, younger individual: The journey of a man from selfish to selfless. But even the movie's effective theme could prove to alienate younger viewers.
There are two cuts of The Wolverine available for viewers, and neither one of them quite matches the intensity (or goriness) of Logan. Even still, whether it's the PG-13 or R-rated version, The Wolverine can be a heavy affair that only gets silly once the big robot samurai enters the picture in the third act.
Chris Claremont and Frank Miller's landmark 1982 run on the title character (called simply Wolverine) was excellent source material for a feature film, but it also has Logan in a pretty dark place. He's grieving, angry, and has little issue showing it. The movie (and star Hugh Jackman) do a superb job of conveying this in the movie, making it a bit more adult than the standard X adventures.
Of all the most recent core X-Men films, X-Men: Days of Future Past is certainly the grimmest. The two films that followed it also dealt with a world-ending threat, but in Days of Future Past annihilation feels not only possible but in progress.
The complex, Nixon-era politics that comprise the vast majority of the film's non-futuristic scenes could also prove outright boring to kids, even if they are arguably the best part of the film for adults. Furthermore, for those parents who don't want their kids to see Hugh Jackman's rear end, they might want to skip Days of Future Past.
Not only one of The Batman star Zoë Kravitz' best films, X-Men: First Class is perhaps the best film of the franchise as a whole. However, there's still some stuff that may be taboo in the eyes of many parents. For instance, there's Kevin Bacon's Sebastian Shaw murdering Magneto's mother in front of him, as well as several underwear scenes with January Jones.
The time period could also prove problematic with younger viewers, as there's an ever-looming threat of global war that fuels the majority of the plot.
X-Men: Apocalypse is close to First Class when it comes to disturbing imagery, but it's of a sillier (more difficult to actually take seriously) variety.
Apocalypse merging a man with a wall is a disturbing visual, but the impact is dulled by poor CGI and the generally cartoonish titular villain. Even with Oscar Isaac under the makeup, Apocalypse isn't very intimidating, and the movie's only truly involving (and perhaps disturbing) scene doesn't even involve him: the death of Erik Lensherr/Magneto's wife and child by the hands of scared neighbors.
Dark Phoenix has an incomplete feeling that makes it hard to keep up, as the film essentially wanders from one scene to the next without any rhyme or reason aside from offing Jennifer Lawrence's character off as early as possible into the runtime.
That scene is the film's most intense, but for the most part, Dark Phoenix is a very bland, very innocuous time at the movies. Jessica Chastain's villain is also an alien inhabiting the body of a now-slain woman, but like the majority of Mystique's wounds it's off-camera.
The New Mutants (at least in terms of the cut that was released) is a movie that tries to be deep and scary, and it barely hits the mark on both accounts.
There's an R-rated cut of The New Mutants somewhere out there, but chances are high that audiences are unlikely to see it, so the theatrical cut is the only one available for rental or purchase, and there's nothing in it that's too disturbing.
Even with the death of major characters like the memeable Professor X and Cyclops, X-Men: The Last Stand has a light tone that goes for entertainment value over the narrative heft that could have made the first cinematic translation of the Dark Phoenix Saga a gut punch (and much better).
That more accurate translation would have also made the film far less appropriate for pre-teens, who should be fine watching The Last Stand and the other two installments of the original X-Men trilogy.
X-Men Origins: Wolverine is far from standing as one of Hugh Jackman's best films, and the same could be said of its standing as an X-Men film. The film is problematic from moment one, but it's also far too cartoonish to be inappropriate for most kids.
Overall, Origins is too silly for its violence to really sink in the way it does in X-Men: First Class or X-Men: Days of Future Past (not to mention Wolverine's two far superior sequels). The movie is based on a comic book, and that's exactly how it plays. With that being said, the final appearance of Ryan Reynolds' (Scott Adkins') Deadpool might be a bit striking and disturbing.
While she's not exactly an X-Men character unlikely for the MCU, Lady Deathstrike (like Wolverine) is a character whose bread and butter is bloody brutality. She displays quite a bit of that (via a memorable performance from Kelly Hu) in X2: X-Men United, but the character's blunt and violent capabilities are hampered by the rating.
With that being said, X2 is less appropriate than the original film for two reasons: Its plot is guided by Wolverine's past torture and Stryker's initial attack on Xavier's School for Gifted Youngsters, which is the film's best but most brutal sequence.
With the exception of the film's WWII-set opening scene, X-Men isn't a film with a surplus of disturbing imagery. Ray Park's Toad has a fairly hideous appearance, but other than that and a senator who gets turned into some goo, the original X-Men is timid.
X-Men also has a nice entryway character in Rogue, the central protagonist in a film littered with main characters. In the comics, she's typically a villain turned X-Man, but the movie takes care to make her a relatable individual, particularly for teens and perhaps even pre-teens.
NEXT: 9 Memes That Perfectly Sum Up Wolverine As A Character