Character Analysis
This Harry Potter film gives us tons of background info on Voldemort's early life, when he was known as Tom Riddle. He was never a particularly nice boy, but this movie does give us a rounder picture of the Dark Lord's beginnings—and maybe even a tiny little smidge of sympathy for him, given how his life started.
He's a Lonely Orphan Who Ended Up at Hogwarts. Wait, That Sounds Familiar…
Yup, young Tom and our boy Harry have something big in common: they both started out life as orphans living in the Muggle world. They both knew they were "different" long before finding out they were wizards, and Hogwarts was probably the first place that made them feel like they belonged.
Turns out, Dumbledore first met Tom at a Muggle orphanage, where he broke the whole "you're a wizard" thing to lil' Tom. That seems to clear up some questions the boy himself had had about why he was so good at making things happen with his mind.
Unfortunately, Tom's magical skillz had already gone to nasty uses. A woman from the orphanage (they don't use her name in the film, but she's Mrs. Cole) who introduces Dumbledore to Tom mentions some strange incidents with the other children:
MRS. COLE: There have been incidents with the other children. Nasty things.
Tom himself cops to some of the not-so-nice things he can do with his powers:
TOM: I can make things move without touching them. I can make animals do what I want without training them. I can make bad things happen to people who are mean to me. Can make them hurt, if I want.
Er, well, we'd admire his honesty, but he doesn't even seem to understand he's done anything wrong as far as hurting other people goes. Yikes, this seems like some pretty textbook sociopathic Dark Lord stuff.
Dumbledore is kind to Tom, but he also makes clear that he knows Tom has been up to no good. He uses a pretty impressive magical fire to reveal a stolen object in Tom's closet. Dumbledore is firm: Tom will have to stop those shenanigans if he comes to Hogwarts:
DUMBLEDORE: Thievery is not tolerated at Hogwarts, Tom. At Hogwarts, you'll be taught not only how to use magic, but how to control it.
(Sorry, Dumbledore, but we're thinking the lesson didn't really stick.)
The Crux of the Horcrux
We learn all this stuff through flashbacks. Well, technically through memories that Dumbledore has collected and thrown into the Pensieve for Harry (and us) to view.
However, there's one memory (from Professor Slughorn) that Dumbledore's had trouble collecting himself, so he enlists Harry to get it. And once he does procure this elusive memory, we finally get a huge detail about Tom Riddle's early life that's key to destroying Voldemort. As it turns out, Tom/Voldy made these things called Horcruxes that have allowed him to divide up his soul.
The upside (well, for Voldemort)? It means the Dark Lord can't be killed as easily—someone would have to find and destroy alllllll the Horcruxes and kill Voldemort for that to happen.
The downside (again, for the Dark Lord)? You have to commit murder to attach the little bits of your soul to objects, and that weakens the soul a fair bit.
It seems that Riddle was totally into the idea, though, and so Harry and Dumbledore have their work cut out for them as far as defeating him goes. We can't even find our keys in the morning, so we're not sure how anyone would possibly find and destroy a bunch of soul-infused objects scattered around the world.
The Road Not Taken
We're not sure from the flashbacks if any other future was possible for Tom Riddle, since he seemed like kind of a bad egg from the beginning. However, maybe he could have been stopped when he was "just" a slightly sociopathic schoolboy.
Unfortunately, we'll never know.