I hired an attorney to defend my wrongful foreclosure three years into my case. We lost... then I looked at my entire case file and it turns out three three years prior he was the banks attorney that initiated the service and foreclosure against me and then switched sides and was going to quash service.

That's definitely a no-no.

But did his conflict of interest affect the result? Foreclosure defense is usually a losing battle anyway. He did buy you three years. That's something.

If his goal was to mask irregularities he committed in initiating the foreclosure, then yes malpractice may have occurred. But his intimate knowledge of the case may have been more of a help to you.