Thomas Jasper Cat Sr., better known as Tom the Cat, is one of the two titular main protagonists (alongside Jerry Mouse) of Tom and Jerry franchise. He is a cat whose breed is still unknown to this day, which is strange considering how long the series has been running. He is mostly bluish gray in color with white paws and a light-blue belly. He also has a tail that is white at the tip. He is sometimes also colored dark blue, but this was only in the earlier episodes. He is Jerry's arch-rival and his best friend.
His antics involve laying traps for Jerry which most of the time end up failing, despite how clever his strategies are whether they work or not, and some of them can get him to occasionally get the best of Jerry and win in the end. He will try to eliminate him in revenge, get him out of the house when he is instructed in doing his job, or even start the fight to a lesser extent on occasions. His love/hate relationship with Jerry existed even as a kitten.
Part of what's said above, however, considering that Jerry is a pest that isn't welcome in his house, makes his actions rather understandable, as it could simply be said that he is trying to do his job as a house cat under his owner's orders. Generally speaking, despite them being the titular main protagonists, both he and Jerry can be classified as anti-heroes as both are abusive, cruel, and villainous at times while antagonizing each other for the sake of getting the best of one another.
In reality though, while Tom may not generally have the best relationship with Jerry and seem him as a huge annoyance, the duo actually have a rather complex relationship, since he's shown numerous time that he shares a secret bond with him, can't enjoy his life without him and can even put his differences aside with him to achieve a common goal.
Some shorts open with him tormenting Jerry despite never being provoked.
Frames Spike for stealing the chicken from the refrigerator and tried to dispose the photos that Jerry took in "Tom's Photo Finish".
Pins the blame on Spike for the mess in the house and his aggressive behavior gets him thrown out of the house in "Spike Gets Skooled".
Terrorizes Nibbles/Tuffy and swats him on the behind with a flyswatter in "The Milky Waif".
Attempts to eat Jerry's animal friends, such as a duckling, a goldfish, and a canary.
Captures Jerry's Mermouse friend to sell her to a museum for money in "Tom's Mermouse Mess-Up".
Attempts to steal gold from Jerry's claim along with Butch Cat in "24 Karat Kat".
He appears as the secondary antagonist of Tom and Jerry: A Nutcracker Tale. Promoted as the captain of the evil Cat King's guard, Tom (along with the other alley cats) crashes Jerry's party, imprisons La Petite Ballerina in a birdcage, and traps the toys. Tom also gathers his troops to try to stop Jerry and his friends from reaching the star. This film may perhaps portray Tom at his most villainous, which adds insult to injury on his character, as he's shown partaking in the entrapment and enslavement of the toys.
In the NES game Tom and Jerry: The Ultimate Game of Cat and Mouse, he kidnaps Jerry's nephew Tuffy and locks him up in the attic trunk, leading to Jerry to come to his rescue.
In the Game Boy Color game Tom and Jerry: Mouse Attacks, he kidnaps Jerry's friends and family (Quacker, Uncle Pecos, Tyke, Tuffy and Muscles) and even imprisons Jerry himself under a cup in a mini game.
Tom: I'm Tom. Jerry: I'm Jerry. Both: YOU TALKED!!! Tom: Well, sure, I talk, what do you think I am, a dummy? Jerry: You said it, I didn't. Tom: Hey, you little pipsqueak, I oughta...Hey! How come you never spoke before? Jerry: There was nothing I wanted to say that I thought you'd understand, and there still isn't! Tom: Alright, that does it, you little... oh, boy, you get me angry!
~ The first time Tom and Jerry spoke to each other.
A cat and a mouse friends? That's disgusting. No way.
~ Tom the Cat.
His name Tom Cat is most likely a parody of Tomcat, a term used for male cats.
While he's usually seen as the instigator of their conflicts, there are times where Tom can be the victim when the conflicts between him and Jerry are instigated by the latter, often because Jerry is intentionally antagonizing Tom for his own amusement.
Both Tom and Jerry, while usually and generally on the good side, can be classified as anti-heroes as both are abusive, cruel, and villainous at times despite being the main protagonists of the series as they typically antagonize each other.