CNN  — 

It’s a lesson many politicians – mostly male – have learned the hard way over the past 15 years: never underestimate Angela Merkel.

The German Chancellor is preparing to step down later this year, having long ago cemented her position as one of the world’s most successful political leaders.

In her time in office, she has dealt with five UK prime ministers, four French presidents and seven Italian prime ministers. When President-elect Joe Biden takes office on Wednesday, he’ll be the fourth American commander-in-chief she’s worked with.