The discrepancy between Raven's behavior and Adam's actual goals/personality can be explained quite simply – she doesn't know him as well as she thinks she does. The primary description of their apparent 'relationship' comes from Raven herself, while Adam has very little to say about it. Considering the whole situation raises the possibility Raven is an Unreliable Narrator and a form of Stalker with a Crush who latched onto Adam as her new Living Emotional Crutch to deal with learning the truth. Especially since Adam shows himself to be a decent and still compassionate person, if a little jaded, (he never expresses hostility towards Lily, helps Eve to as much as possible and only fights her after she initiates it, and is clearly accepted around Xion even though being kind to the citizens had no real benefit to him), it's possible he tried to reach out to her and unintentionally sparked her obsession—which is another familiar (and realistic) trope. It's also not uncommon for those with obsessive behaviour to imagine they have deeper relationships with their targets, or that they're sending them subliminal secret messages. Adam may have seen her as an ally and possibly a friend, but there's a real possibility Raven deluded herself into thinking she was his exclusive right hand who 'knew him better than anyone else.'
The difference between the limb damage that Raven takes compared to Tachy is quite noticeable, with the former looking much more mechanical than the latter. This makes sense since she's only from the 2nd Airborne while Tachy and EVE are from the 7th. The latter are using much more advanced Andro-Eidos bodies that are much closer to actual humans, featuring more organic parts.
Raven's capture of Tachy to turn her into an Alpha makes you wonder if this is something she's done before. Not only was her attack clearly meant to capture at least one 7th Airborne Squad member, she clearly planned it so that she would only have to face an already tired EVE and Tachy. At the same time, with five previous missions taking place before, one can't help but wonder if Raven also tried this with those and if any previous airborne squad members had been forcibly turned into Alphas and if any of their squadmates had been forced to kill them. That Adam knew exactly when to come to rescue EVE does seem to indicate that he knew what Raven was up to and wanted to stop her, possibly because he'd seen the outcomes of the previous times she did it.
The point at which, whether it was earlier or just before the events of the game, Adam must have realised that Raven had lost her reason and was consumed aggression and hatred… Given that he'd had to watch the other Naytiba suffering the same fate, that must have been quite the gut punch, and would likely contribute to some of his more jaded, depressed streak over the course of the game. Of course he's struggling to be optimistic about the odds—the last time he's tried to help people on his own, it's turne dout very badly.
