A man shelters from the rain under an umbrella as he walks past the Euro currency sign in front of the former European Central Bank (ECB) building in Frankfurt am Main, western Germany.Kirill Kudryavtsev | Afp | Getty ImagesEuropean banking's latest takeover battle is widely regarded as a potential turning point for the region — particularly the bloc's incomplete banking union.Italy's UniCredit has ratcheted up the pressure on Frankfurt-based Commerzbank in recent weeks as it seeks to become the biggest inv ...