Prosecuted Noriega, Lockerbie and John Gotti. Threatened to quit, with Comey, back in 2004 if GWB tried to keep the warrantless wiretapping alive. Served as director of the FBI under Bush (2 terms) and Obama (first term). Has focused on cybersecurity since 2013.
I have a lot of unresolved angst about the Bush years but I don't remember Mueller as one of the bad ones.