No Chiara, this is only YOUR point of view, discussed many times through other topics, many people don't see Ostagar as a betrayal and to me it wasn't one, it's called tactical retreat.
Hey, you're the one who played the "intelligent" and "logical" card, so I played my own "I can choose not to spare him for the same logical reasons" card.
But yeah, let's sacrifice all the soldiers in a battle lost in advance, just in the name of honor, everyone will be happy to die for nothing.
The game never confirms that Loghain is right about that, so you choosing to believe him doesn't make you more right than one who says, "Uh huh."
Any chance I had of believing him about the horde was dashed the moment he decided to withdraw all troops from the south and then leave the south wide open for darkspawn for months on end. Interesting how when it comes to Ostagar, the horde was too huge and powerful for Loghain to defeat with the combined efforts of his men, the king's men, and the Grey Wardens... but it's not too huge or powerful to allow to pour into the unprotected countryside and ignore for months on end while he consolidates his own power in a civil war.
And he is a very loyal Warden once you have him in the team
Stop right there. The Warden doesn't know Loghain will be loyal to them at the time that they need to decide whether or not to spare him, so "after the fact" information doesn't justify the "in the moment" decision.
At the time that the Warden needs to decide whether or not to spare him, Loghain has betrayed and abandoned every ally he ever had. Promised to help Cailan and the Grey Wardens at Ostagar, but left them to die instead (and immediately usurped Cailan's throne and made the Grey Wardens the scapegoat for his withdrawal for good measure). Promised to support Uldred and his mages, but abandoned them to the Templars instead. Promised Isolde he'd get a tutor for her son, sent an assassin to poison her husband instead. Promised Jowan he'd help him with the Circle after he poisoned Eamon, but left him to Isolde's "mercy" instead. (Whether or not the Warden chooses to free Jowan doesn't matter. It doesn't change how Loghain used, promised to help, then abandoned Jowan.)
He also consistently showed disrespect to the Grey Warden's authority as darkspawn experts, didn't take the darkspawn seriously as a threat (continued to insist that it wasn't really a Blight all the way to the Landsmeet), and consistently insisted that an "eventual" invasion by Orlais is the greater threat than the omnicidal horde slaughtering and eating and polluting its way through the countryside, even as half the nation falls to the darkspawn. He's proven to be unstable, untrustworthy, unreliable, and damn incompetent against darkspawn all game, and hasn't really admitted that he was wrong or shouldn't have done what he did all game, so I don't have any logical reason to trust him or rely on him.
I may be sore with Loghain for enslaving my friends and family after crying "I was a slave!" most of the game and hypocritically rationalizing elven slavery with human freedom... but even putting all that aside, I thought, "Could I logically spare Loghain anyway?" And I thought, "No, I don't ****** trust you. You haven't given me a reason to trust you."
Loghin has only proven he's not a good team player, so my city elf doesn't want him on her team.
I think that some people whose warden got dumped by Alistair even if they killed Loghain (so, being dumped because the warden is not human noble) might see that as a betrayal, in a way. Everything depends on your point of view and your choices.
Of course a lady elf would feel bitter to be dumped by Alistair just because she is not human and not noble enough.
So, spare the guy who allowed the slaughter and enslavement of your family and friends just to spite your boyfriend because he dumped you?
That's catty.
33% more people who can kill the Archdemon isn't compelling?
Not one who's proven he can't hit the broadside of a darkspawn horde when it's right in front of him, no.
Not one who chose to ignore the threat of the Archdemon in favor of battling the imaginary threat of Orlai for over a year, no.
Not one who's gone against orders and decided to deal with the darkspawn his way and nearly gotten everyone killed as a result, no.
Not one who's proven to be an unreliable loose cannon who's dealt more damage to "our side" by friendly fire than the entire darkspawn horde in the past year, no.
Not one who's never really conceded that he was wrong or admitted that he shouldn't have done all of the above, and therefore can likely do it again since he hasn't proven that he's learned his lesson or won't pull the same tricks in the future, at the time that the Warden needs to decide whether or not to spare him. Which is just after defeating him in a Trial by Combat because he wouldn't hear of anyone saying, "The Blight is the bigger threat" or "Grey Warden are NOT Orlesian spies! LET IT GO!"
One extra cannon doesn't really help the cause much when it's a loose, friendly firing cannon.