Lol at people thinking they can kill Solas. The Evanuris (which he's part of) can't be killed so easily. The most you can do seal him up. Murder knifing him is an option, but futile.
Honestly, what makes him different from Corypheus? Corypheus did what he thought was right, he was just a loyal priest hoping to bring back the Old Gods. He woke up to find his nation on the verge of collapse and that he unintentionally brought the Blight and might've been deceived by the Old Gods.
He's fighting to restore Old Tevinter just as Solas is fighting to restore the Old Elvhen Empire.
Solas will use all those Elf soldiers and dispose of them just like he did with Felassan "The slow arrow breaks in the sad wolf's jaw" - Cole.
You can argue that "he feels sorry" for doing it, but the same can be said about what little we know about Corypheus: he felt sorry that he's going to bind the Drinker of the Well of Sorrows, especially Calpurnia. But it was all for the greater good.
Time will tell how he'll use his elf army though I doubt it won't be any different from Corypheus ... he'll actually know how to use all these ancient magic/ devises for one thing.
Solas has such a low opinion of the world that even if the Inquisitor's generation is able to convince that they're worth saving, what about future generations? There's nothing stopping him from doing it again.
He could have taken a page from Mythal and still help The People who call to "Asha' Bellanar" what's even more interesting is that Flemythal still refer to elves as The People which says alot
The main difference between them is characterization.