Well let say I am moral flexible and I am good at arugments because I point out every single detail on a person and I will use all that person history to win the arugment at any cost will that make me a good lawyer?
No, that makes you an [censored]*.

When you try to win an argument by attacking the other person's character (or history), you're making an http://en.wikipedia.org/wiki/Ad_hominem ([censored] yeah, pretentious latin) - you're not addressing their argument at all. People still do it, of course, but that doesn't make it a good tactic.
What will make you a good lawyer is being quick-thinking, charismatic/persuasive, good at structuring ideas, skilled at picking out details - basically being able to present a convincing argument. Being morally-flexible won't make you a better lawyer, but you will find it easier to live with yourself if you end up in a lucrative career being financed by people who probably don't deserve your services.
EDIT: Oh yeah, above poster makes a good point. Being a capable writer is absolutely essential.
*Sarcasm, treat with caution. May contain nuts.