There should be a point where you draw the line for excuses for a character. I am dead serious when I say Xin Zhao probably had more determination than 200 people, and he still practically dropped dead. This isn't assuming so much as letting Riot do whatever the hell they want with a character with little to no development. We are simply told Vayne tragically lost her rich life and suddenly she becomes badass chick who can fend off mind**** magic? Sure determination is a powerful motivator but...tell that to other 72 champions that have gone through the same **** and seem to have just as much determination, if not a better goal.
Yes, we don't quite have the history on where and how Vayne learned how to fight, but we can assume it was like other vigilantes: through self learning and seeking out the techniques she wanted/needed to accomplish her goals.
And how can you justify that Vayne's goal isn't as good as the other champions? Most of them are selfishly driven (yes that includes some of the "good" characters). I'll take a favorite of mine, Master Yi.
No, his goal is not just to preserve Wuju. It is also to enact revenge against the people involved in the death of his village. He is driven by revenge, Vayne is driven purely through justice. Doesn't that make her goal "better?"
Don't use loaded words in your argument.