There are two ways to approach the finale - the violent and the peaceful one, that depend on whether or not you cross the Rubicon. If you go violent, it goes about the way you'd expect - you take Rome by force, kill a lot of people, take the bad guy's head. One of the companions ditches you and even turns against you, but it's incredibly easy to make him switch sides back to you. The game makes a big deal about you having to dispose of Cato, Cicero and Pompeius, but again - you can effortlessly convince them to stand with you, or at least stand aside and let you do what's necessary. There is no actual human cost to betraying the republic and declaring yourself dictator, aside from a bunch of nameless, faceless NPCs. You can also flee to Egypt or get crucified, but I have no idea what kind of cuck would cross the Rubicon with an army and then not declare himself emperor. Caeso is upset with you and moves to Egypt, but he moves to Egypt regardless of which ending you pick. Julia is also mildly upset and leaves Rome, but eventually she returns.
Meanwhile, if you decide not to cross the Rubicon, the game starts off with killing of Syneros, the cool old guy who's always been on your side. After that, your villa is set on fire. Then the bad guy takes your entire party hostage, and you have a choice between saving them (and being branded a criminal, because you've just killed a consul) and watching one of them die (in my case, it was Caeso, I don't think there's any variation as to who dies) before the crowd has enough and tries to get some mob justice done. If you do save Caeso, you need to either flee to Egypt or get crucified. If you sacrifice him, you can either become a consul or retire to a farm. Regardless, the tone of the ending tries to be triumphant - you saved DEMOCRACY! - but the game makes a giant presumption that democracy is worth preserving because it just is, and is worth this huge human cost that preserving it requires.
In the end, the real choice in Rome is between getting personal power, wealth and fame, becoming a beloved and effective leader and making Rome great again (at the cost of making Caeso not even upset enough to try and assassinate you, boo fucking hoo), OR preserving muh democracy, but losing the people you care about. I'm sure that maybe for some people more in love with the ideas of the republic that's a real, difficult choice, but I'm just baffled. In Viking, you could become the ruler of the Danelaw, but it required you to turn on two of your companions (and potentially even kill them), turn on two people you've been helping the whole game (and potentially kill them), and through the whole sequence you're being called a power-hungry traitor and murderer, because that's exactly what you are. Rome kind of tries to do the same, but it doesn't work - in Viking you don't really have a righteous reason to go for the violent ending, while in Rome you do - after repeatedly trying the political, socially acceptable solution, you get sick of it failing and try to finally get things done. You get called a traitor by either people you can easily convince to choose your side, or by the villain of the game, who cheated, robbed and murdered for 40 hours of gameplay, so both sides feel kind of hollow.
On the flip side, Rome does get one thing better than Viking - both peaceful and violent endings have engaging gameplay and story, while in Viking, both routes were completely the same, except peaceful route lacked about three hours of cool violent gameplay.
