I will supply you with some character information and some context for my specific project, though I'm thinking my question could be relevant for almost any story.
I am writing a story involving with a "bad boy" main character "X" (hero) and a female character "Y" (to-be heroine). I have a clear idea of the hero and his place in society: Very wealthy for his age (inherited fathers company). Perceived as somewhat of a womanizer, In my opinion he's misunderstood. I plan for the two characters to fall in love at a later point in the story. Before that however, I want the hero to go through some challenges/struggles before eventually ending up with the heroine.
As of now, there are some "romantic" issues: "X" has an affaire with B, B is separated from C, C is interested in "Y" and "Y" is also being charmed by ex-boyfriend E..
Aside from the romantic issues, I'm having trouble coming up with challenges/issues that make sense for the hero to go through/solve.
So; I am not looking for answers regarding my specific plot, but rather a broader answer to the question:
How do I figure out what challenges fit a character?