That depends on your definition of "good lawyer" and "successful lawyer".
And that depends on answering the question "what is morally right and what is morally wrong".
And here we are writing a philosophical book in one comment.
The question is bit broad, isn't it? =)
hi :) that's why I asked about your definition :) The question is broad, I totally agree, but I think this is better than question with answers 'yes' or 'no'.
We often think that it's hard to talk about law because it always depends on our morality, but it doesn't mean that we shoudn't do it :)