Truly a great action film - Tom Cruise at his best. With that said, plot holes always bother me.
1. If you're a savvy spy who answers to no one, you don't tell the head US guy, who has unlimited global resources to eliminate you, that you are going to do the complete opposite of what he wants. Just lie to him and then do what you are compelled to do.
2. If you are very seasoned MI6 former agent chasing the bad guy to a bridge in Venice,and he has a knife and you have a sword, you don't close the distance when you fight... you use the sword like a sword.
3. Bad guy kills the train engineer and fireman and locks the train in full speed. That steam locomotive needs 15 lbs of coal a minute to keep running. The train would have run out of steam in a few minutes and come to a stop.
I know, I know... it's a movie. And a great one.