Takara's take on the Headmasters (i.e. making them more like they were in the anime and cartoon), a huge step up from Hasbro's newer decos, or just expensive pandering to the G1 crowd?
While the updates to the Headmaster figures have been largely praised, the Titan Master gimmick being applied to other figures has lead to arguments. Some feel like it's not a big deal and the critics are just being the fickle They Changed It, Now It Sucks! fans that they've always been, others feel the transforming head gimmick is intrusive and feels that it clashes with the characters who weren't originally Headmasters.
It's the Same, Now It Sucks!: Titans Class Fortress Maximus, this line's centerpiece, has come under fire for being a Metroplex retool. Though it's a very extensive retool of Metroplex it's still criticized for keeping too much of the core engineering and transformation as well as lacking Fort Max's weapon loadout. As the Titan Class line expanded with other heavily requested "big" figures, Fort Max ended up being overshadowed and is often considered one of the weaker releases.
All of the "Master" (Targetmaster, Headmaster, Powermaster) series being condensed down into Titan Masters (which are the Headmasters). Many lament the loss of the gun and engine combiners and dislike how they were given detachable heads. Somewhat lessened with single-pack Titan Masters (in North American and Europe) or Deluxe class figures (Takara's Japan release) including Titan Master scaled vehicles that turn into weapons, while weapons with Titan Master cockpits (available with any Deluxe and larger) somewhat revived the Targetmaster idea. That they get a "combined" mode with their head components sweetens the pot, but many still wish Powermasters got any attention.
Turning several characters who weren't originally Headmasters into Headmasters, especially by those who view the whole gimmick as intrusive. The fact that not all of the original Headmasters would be getting new figures has only fed these complaints. Further complicating the matter is that despite the gimmick supposedly being intended as universal, each Titan Master is designed independently and may not fit properly on other figures (or any, in the case of single-pack ones). It can sometimes be fixed by turning the tiny figure's own head around, but then the neck socket may damage any face paint there might be.
Hasbro's sudden inclusion of stickers, after years of not using them (with a few exceptions). While the Titan figures included them due to extensive paint decos potentially making them excessively expensive, most normal retail figures have used painted details since 1996, with the few exceptions being barcodes or large, complex images. Then, suddenly, Optimus Prime and Megatron, leader characters both in the larger Voyager class size, not only have stickers but foil ones that fall off easily and clash with the color scheme. This was after the international collector market threw lots of shade at Takara for doing the same thing for their Transformers Prime and Robots in Disguise (AKA Adventure) toylines.
Sentinel Prime. Some think he's a pretty good villain who hits all the high notes (hammy, hatable, cool) with a neat design and a simple but effective evil plan. Others feel Sentinel Prime reeks of a "been there done that" feeling, as he's just the Fantastic Racism of Nova Prime with the Authoritarian leanings of Zeta, and a design that was very obviously supposed to be Astrotrain. It's a toss up between those that feel he's similar and that it's not a bad thing, and others who feel that he's just uninteresting and derivative.
Infinitus's existence is essentially an extension of Sentinel's Broken Base. Some really liked the twist that Sentinel himself was never real in this continuity he was just a persona concocted by Infinitus. This was considered a pretty good way to detach Sentinel from the generic "Evil-Prime" that all the other non Optimus Prime's fell under. Others felt this aspect was underplayed and Sentinel just came across as the standard evil prime, except with a Headmaster gimmick.
Broken Base: Tying in this series to Revolution (2016). Does it make sense, seeing as Revolution was occurring concurrently, or is it just confusing and distracting?
Continuity Lock-Out: In contrast to Combiner Wars, Titans Return relies quite a bit on the plot threads that have been set up in previous books (Optimus's conquest of Earth, Red Alert and Fortress's activities on Luna 1, etc.). It can get quite confusing, especially when it was revealed that the books also tie into Revolution (2016).
When Prowl shows up, Fortress Maximus immediately attacks him. Cerebros tries to stop him while asking why he's so angry. Maximus tells him to ask Prowl. Prowl thinks... And thinks, saying that it's probably going to take a while given just how many people he's pissed off over the years before launching into a very insincere generic apology. And then he finally remembers. And he doesn't actually tell Maximus the truth, that the whole purpose of the op was to cover up Prowl's dirty secrets, not a rescue mission, since Maximus probably would have actually killed him upon hearing that.
When Prowl says that the Brainwashed and Crazy Red Alert just shot him, Fortress Maximus's only response is "living the dream."
Sentinel Prime's plan is ultimately stopped by Prowl's table flipping skill.
Moment of Awesome: Red Alert manages to free himself from Sentinel's control by imagining (or remembering) a conversation with the Autobot psychiatrist Rung, which enables him to figure out what had been done to him and how to overcome it.
The start of episode 7 has Victorion materialize in front of Trypticon in search of Overlord and then completely fail to notice both the giant robot dinosaur behind her and the giant laser above her head until after Trypticon attacks her. As a review from Seibetron.com put it...
"I didn't think is was possible to get ambushed by a 150-story kaiju, but here we are."
Trypticon's transformation into base mode being concealed by him being engulfed in smoke from the explosion caused by the combined efforts of our heroes is a clever if unnecessary way to avoid animating his transformation. Having smoke appear from nowhere when he transforms back is more laughable.
Rescued from the Scrappy Heap: While fans are divided on whether or not this makes her a good character, many feel that Windblade's portrayal has been improved over how she was portrayed in Combiner Wars by having her drop the Knight Templar aspects and mellow out to be closer to other versions of the character.
They Wasted a Perfectly Good Plot: While this series is a step up from its predecessor in that the titular Titans are much more prominent and integrated into the story compared to how Out of Focus the combiners were, the other aspects of the Titans Return toyline are pretty much ignored. There is only one Titan Master who never turns into a head (despite having Cerebros' face on his back) and the Headmaster elements of characters with compatible toys are never addressed.
Unexpected Character: Considering this was a Hasbro-sanctioned outing, Fortress Maximus breaking out the Master Sword in the last episode caught half the fans off guard.note Though this may have been foreshadowed by a convention-exclusive Fortress Maximus toy coming with that very weapon.