To modern readers, Aeneas can seem like a bit of a tool. We mean this in both a non-technical and a technical sense. In a non-technical sense, Aeneas is a tool because can come off as a bit of a jerk. At least, this is what it might seem like when he first shacks up with Dido, giving her the impression that they're married, and then suddenly sails off on his mission, telling her, "Sorry, gotta go. And hey, it's not like we're married or anything." When he meets her in the underworld, he tries to strike up a conversation like it's all no big deal – and then tells her again that it wasn't his fault. Come on, Aeneas, even if it wasn't your fault, you could at least show a little bit more empathy! Don't you know that the bigger man admits when he's wrong?
Aeneas's not-so-nice side reveals itself again in Book 10 and Book 12, when he kills various guys (including, finally, Turnus), who are surrendering and begging him for mercy. OK, so you were really angry that Turnus killed Pallas, but still, don't you remember your father telling you to "spare the conquered"? Is that really the example you want to be setting for your son Ascanius and the countless generations of Romans who will come after him?
That was the non-technical sense in which Aeneas is a tool. Interestingly enough, the technical sense makes the non-technical sense seem not as bad. (At least, this seems to be the point of the poem, so we tender-hearted moderns just have to find a way to wrap our heads around it.) Aeneas is a tool in a technical sense in that he is an instrument of fate. He didn't up and decide to go off on a mission to found a new city: it was the gods who put him up to it.
Deep down, Aeneas has feelings too – including feelings for Dido – but he knows that he has to smother those feelings in the service of a higher cause, just as he smothers his feelings of grief for his lost companions when he puts on a brave face for the survivors in Book 1. This is what he's getting at when he tells Dido, "I sail for Italy not of my own free will." Basically, Aeneas knows he's being a jerk; he just also thinks that that's the right thing to do.
In the first half of the poem, Aeneas is dedicated to his quest, sure, but he's still a little uncertain about it. (This uncertainty might factor in to his jumping into a relationship with Dido.) On balance, he seems to think that the positive aspects of his life are outweighed by the negatives. You can tell he's feeling this when he asks his father Anchises in the underworld why anyone would ever want to be reborn after they die.
Book 6 marks a major shift in his character, though; after Anchises shows Aeneas all the cool stuff that later generations of Romans will do, our hero suddenly becomes really gung-ho. This new enthusiasm is what carries him through the rest of the story. Whether this new enthusiasm plays a role in him losing control over his emotions at the end of the poem is up for you to decide. On the other hand, there are certain things about Aeneas that don't change. These are his unswerving loyalty to his father, Anchises, whom he carries on his back out of the burning Troy; his son, Ascanius; and whoever has been put under his care. Nobody can dispute that these are the qualities of a pretty stand-up guy.
Dido is many readers' favorite characters in the Aeneid, and with good reason. It is clear that Virgil spent a great amount of energy developing her character, and the extended description of her and Aeneas's doomed love affair in Book 4 represents one of Virgil's significant innovations in the genre of epic poetry.
For the earliest precedents to the character of Dido, you'd have to turn to the sorceress Kirke (or Circe) and the nymph Kalypso (or Calypso) from Homer's Odyssey. These women, especially Kalypso, who is holding Odysseus prisoner when the story begins, play a similar role in the plot of the Odyssey as Dido does in the Aeneid: they distract the hero from his main mission of getting home (Virgil puts a different spin on this in the Aeneid by making Aeneas look for his new home.) A more immediate precedent for Dido is the character of Medea in the epic poem The Argonautica by Apollonius of Rhodes. She is similar to Dido in that she is made to fall in love with that poem's hero, Jason, by Eros, the Greek god of desire – just as Dido falls in love with Aeneas because of the influence of Cupid, the god of love.
That said, Dido's character in the Aeneid surpasses all of her precursors in complexity and humanity. For one thing, when we first meet Dido, she is already a widow. This distinguishes her by giving her a meaningful past that continues to influence her in the present. As a result of the murder of her husband Sychaeus, Dido has had to flee from Tyre, her home, to North Africa, where she now supervises the building of the new city Carthage.
We know that her fledgling kingdom is surrounded by enemies on all sides, and you've got to admire the guts with which Dido determines to hold out against all odds. (We see evidence of this in the increased security she has put in place along the coastline that hassles Aeneas's shipwrecked comrades.) A different sort of threat comes in the form of offers of marriage – for example, from the neighboring North African King Iarbas. So far, she has refused all offers of marriage, determined to remain loyal to the memory of Sychaeus.
But that's just the issue: she is loyal to his memory. Thus, the first thing that Amor, the god of love, does when he sits on her lap in Book 1 is to destroy her memory of her husband to make room for Aeneas in her heart. (This is one of those interesting points where you could argue that the god of love is just acting as a metaphor for what we would understand as the ordinary, psychological process of love, which can also make us forget old attachments. What do you think?)
By the time Amor has finished doing his work, Dido becomes one seriously passionate lady – Virgil describes her feelings of desire as like a fire burning in her marrow. After she and Aeneas hook up in the cave, Dido regards herself as married to the Trojan warrior. That is to say, she is now completely committed. When she learns that Aeneas is leaving, it is earth-shattering – and it is then that the memory of her old husband Sychaeus floods back, filling her with shame. It is in this state that she commits suicide and hurls her vindictive curses at the Trojans. It is also significant that, when we see Dido for the last time, in the underworld, she refuses to speak to Aeneas (or maybe she can't?) and goes to stand with the shade of Sychaeus.
The Rutulian warrior Turnus represents is different from Aeneas in a lot of ways. He's brash, hotheaded, and seems to care only for himself. That said, he is also an extremely courageous warrior, doing stuff Aeneas seems to have outgrown since the fall of Troy made him take a good hard look at himself and decide to become a responsible leader for his people. For example, you've got to give Turnus major props for running into the Trojan fort alone and taking on the entire garrison. Then, apparently in full armor, he throws himself into the Tiber river, just to avoid being killed or captured.
Another thing Turnus seems to have that Aeneas doesn't show much of is a capacity for passionate romance. Sure, Aeneas showed his sensitive side for Dido…while trying to get her to stop crying about him abandoning her and claiming they weren't married. But Turnus really feels his blood boiling when he sees Lavinia blushing in front of him. In fact, he gets so mightily aroused that he decides to…go off and kill some guys. OK, maybe this is less like romance and more like good old fashioned lust. And maybe lust for the power that would come with a marriage to Latinus's daughter has something to do with it. Turnus certainly shows his greedy side when he takes the ornamental belt from the corpse of Pallas.
Turnus also gets himself into hot water in the classic (make that classical) scenario of the guy who can dish it out but can't take it. This is because, after refusing any possibility of accommodation with the Trojans, or of accepting a less prestigious woman as his wife, Turnus pretty much guarantees that he's going to have to fight Aeneas one-on-one. When it actually comes down to it, though, Turnus doesn't stand a chance. Maybe we're being a bit hard on him here, because there was a bit of bad luck involved, what with him having the wrong sword and the gods backing up Aeneas.
Still, he doesn't come off very well when, just before Aeneas is about to kill him, Turnus suddenly remembers that he has a dad – after not seeming like the slightest bit of a family man up until now – and tries to use him as an excuse for Aeneas to spare his life. We're not saying that Aeneas was justified in killing Turnus, but the Rutulian warrior still doesn't put in a very good showing.