- Does the character work as a character?
- Does the character achieve what they wanted to achieve? If not, is what they achieved better or more appropriate than what they originally thought they wanted?
For a character to work as a character, they've got to be well drawn. Flaws, virtues, a good knowledge of what makes them tick even though you almost certainly won't share all of that information with your readers and they've got to be memorable for some reason. This applies to characters who are not necessarily in the starring role as well. For example, I always recall Sam Gamgee from The Lord of the Rings for his absolute loyalty to Frodo Baggins.
There has got to be something about your characters that grabs your reader's attention and generates emotion for that character (this can be hatred as well as love. Sauron grabs my attention but I certainly don't like him. I feel sorry for Frodo and am rooting for him to succeed in his mission but there is something appealing about his character that makes me want to root for him. A less likeable character, though I'd still want the mission to succeed, would not have so much whole hearted support).
As for achievement, this is the pivot for any story. Yes, Frodo achieves success but at a high cost. (And if you haven't read or seen The Lord of the Rings by now, you really should have done). Yes, Sauron achieves his success in creating that ring but loses it... meaning the achievement to retrieve it (for use or destruction) is the ultimate goal. Characters can also judge whether they've been successful and this will vary. A pessimistic character will set themselves standards they can't possibly meet so will always fail. A more optimistic one will make the best of a bad job. There are so many stories to be told from characters like that. Achievement then varies. And how it is judged can too.