Forcing your mind down a channel that it normally doesn’t take is difficult for a lot of people, so for anyone that’s seen 500 Days of Summer it might be likely that some think that Summer is the antagonist since she gives Tom such a chilly brush-off at one point, but in truth, Tom isn’t entirely innocent throughout the movie, and there’s a reason behind this. In fact, even Joseph-Gordon Levitt agrees that Tom was more of an antagonist than Summer ever was, though if one wants to look at things from a purely neutral stance there isn’t really an antagonist in the movie, it’s far more comfortable to assign such roles since otherwise for some folks the fabric of the story starts to tear and rip apart if they don’t have firmly assigned roles. For the sake of it though, let’s assume that Tom was the bad guy, which isn’t too hard if one really stops to think about it since no matter how Summer was acting it was in response to how Tom built her up and then tended to obsess about the idea of her rather than the actual person she turned out to be. There are those moments that happen when a person doesn’t know someone well enough but believes that they’re in love with them when in truth they’re in love with the idea that they’ve created in their own head and have used to surround the person when in real life the person that they’ve decided to lock onto is likely quite a bit different.
Summer even went so far as to tell Tom that she wasn’t ready for anything serious, which in some ways is a dodge that’s used to dissuade people from falling in love or from becoming too attached, but is also a justifiable method that some people use since they happen to be looking for the right person but might find someone that they’re able to laugh and have a good with in the meantime. It sounds terrible to use another human being as a waypoint or a place holder until an individual finds ‘the one’ that they’ve been looking for, but it’s done quite often, as this is how a lot of relationships end up forming. People want comfort, they want to know they’re valued, and they want someone in their lives to have fun with when possible and to just sit and talk to when they need someone to understand how they’re feeling. It’s a very big comfort thing and not meant to be too personal at all, but individuals like Tom, who dive headfirst into something that looks like a relationship, tend to take things way too seriously from the start and end up devastated when the person they’re attracted to doesn’t love them back in the same way. This eventually leads to the misunderstanding that the person they’re in love with is being cold, emotionally distant, or even just cruel. It’s true that some people do manage to become unbearably cruel in this manner, but it’s also true that Tom simply took things too far too fast in his own head and built up an idea of Summer that didn’t completely correlate with the real person.
Whether this makes him a villain or not is a bit subjective since really, he’s a guy that wants to fall in love, and Summer laid out what she wanted and didn’t want pretty early on. He might have listened to this, but he didn’t hear it. There’s a very big difference between listening and hearing, as a person that listens can say that the words registered, but a person that hears everything that’s being said is someone that grasped the overall meaning of what they were being told. Hearing is all about comprehension, understanding, and gives way to the ability that people then have to adjust their lives according to what was heard and to react to certain stimuli in a way that makes the most sense for them. If Tom heard anything that Summer said to him then his initial response was still in error since the fact that he was devastated when they parted ways means that he put too much of himself into a relationship that wasn’t going anywhere, and hung on up until the moment he found out that she’d been married. This is a pretty common occurrence that can happen on the dating scene and it’s something that each person learns to take in stride in their own way.
In reality, neither Tom nor Summer are the villains of this movie but again, it’s more comfortable for a lot of people to recognize certain roles and just go with it. But as far as who went too far in thinking that there was a solid relationship between the two of them, Tom was definitely the one that stepped over that line.