The best - Wonder Woman, Catwoman, and Talia, all bring something new and interesting out of Batman.
Diana has the same resolve that Bruce has, but without his baggage. She's able to fight for justice and champion the meek without becoming a dark symbol of fear. She brings levity and hope out of him. Unfortunately for him, he's really just a stand-in for Steve Trevor.
Selina brings out Bruce's playfulness. Basically, whatever veneer Bruce wears publicly to come off as a playboy is less of an act with Selina. He's more lustful, reckless, and generally irreverent when he's with her.
And Talia represents Bruce's adventurous spirit - a wild and epic temptation that Bruce wants more than he'd readily admit. The reason it doesn't work is that both Talia and Bruce are incapable of compromising on their life's mission.
Also, shout-out to Jezebel Jet, who managed to legit get the best of Bruce and only failed because Dr. Hurt couldn't keep up his end of the bargain.