Made me laugh to hear my younger than me French voisine saying 'mer credi' and 'punaise' in much the same way as some polite English speakers say 'sugar' etc.
Sadly, with growing age and anger, I find myself using the 'F' word more frequently but hate to hear it from others.

Very prevalent in TV films these days too.
Less strong English curses nowadays are 'Bloody' which really in origin was much worse because it was the blasphemous 'By our Lady'. 'Blimey' and 'Crikey' similarly.
In French I often use 'putain' involuntarily.