She didn't do it for every performance (only most of them, you know), but when she had to Bette Davis could bring a certain high-electrical charge to a character that would make a movie more dramatic. It's there in Dark Victory, and she finds with the character of Judith moments to make that energy go really up, and then other moments to tone it down a little more - in a sense this is a performance that is great because of her fluctuating energy levels, if that makes sense. For example, her character discovers, as does happen sometimes (or only most of the time) in such dramas, about what her condition really is by doing just a little bit of digging - her file is on the desk that Dr. Steele happened to leave behind while things are being packed away - and she sees "Prognosis Negative." Just in case we don't notice that enough, the director helpfully takes those words and blows them up.
She has a confrontation with Dr. Steele, who she's growing to like a lot before this and he may be falling in love with her too, but it's not an immediate "How could you!?" type of scene; she's out for a night at the club with Steele (Brent) and her friend Ann (Fitzgerald), and she's being a bit uncharacteristically nasty in front of them. Judith's shown up till now she can be a little fiery and direct when talking to people - it's the Bette Davis way, from a number of her characters, just the way she talks and looks at people - but this emotion is different, how she has sarcastic comments and snide remarks as they're looking at the menu for what to eat. She picks hers up and goes (and I'm paraphrasing here), "Ah, shall we have some 'Prognosis Negative'!) And then the cat's out of the bag and things click for the other characters, but this whole scene is indicative of what Davis could do so strongly - we feel angry for her that she's been lied to (though one might understand on the other hand trying to hide the 'There's nothing we can do' sort of melodramatic news involving a medical condition, as Judith has). It's everything behind Davis's FORCE as an actress that does it in that and other scenes here.
What's also good about Dark Victory is that Davis gets to show vulnerabilities as well, mostly in the last section as her condition starts to worsen (come on, I don't think I'm giving anything away as far as the plot goes, what's to discover here is the emotional range of things), and her strange going-blind-in-one/both-eyes-brain-falling-apart disease makes her rely on others, but she's not doing it so much that it becomes maudlin. We also come to believe the romance between the two and not simply in that 'you're dying, I'll care for you, etc' sort of way from the doctor, though that's there; I can sense the connection between the actors (Brent I think was a typical contract player for the time, and really this is Davis's show so everyone else are just that, including Bogart and Reagan), and they have good chemistry.
Does it get melodramatic? Oh, you bet your life it does. This is meant to draw the tears out, whether you're a woman who's seen it many, many times, or the man who got dragged along (though maybe he wants to see it too) to see the high dramatics unfold. But the writing of it is clever to dole out the details gradually, that the inciting incident, of Judith having the "WTF" moment as she's riding her horse, is startling and harsh, but how characters discover things and then find them out (again, that folder-file scene, and the confrontation after) is told like... well, one of these kinds of stories should be. It's before this sort of tale got over-used and over-wrought (Love Story, I'm sure, is a relative of this even distantly). It's all about Davis though, at least for the most part.
And yet, I don't know if it's entirely a *great* movie unto itself, even as Davis surely is; Bogart plays the "Irish Brogue" and his accent goes in and out, so while he tries he's kind of a weak spot in the story for me, as the stable hand who may have feelings for Judith as well; Regan may actually be okay here since he's just playing a drunk playboy, but even at that he's not terribly convincing; there are some scenes here and there in the first half where it could use a little tightening, and it's really halfway through where the writing gets tighter still. But there's a lot to like about Dark Victory, as it understands what movie it's got to be and manages to get a lot out of the audience.
At the heart of it is Davis and Judith, that woman who will look on at this as a 'victory against the dark.' It's almost inspirational, if one can see something like that out of a situation as grim as a dying with dignity, or if that's what it even is. 8.5/10