The choice of "excuse me" or "pardon me" is largely regional. I grew up with "excuse me," but switched to just "pardon" because it works in French and Spanish t

The choice of "excuse me" or "pardon me" is largely regional. I grew up with "excuse me," but switched to just "pardon" because it works in French and Spanish too. If it is meant rudely or not is entirely based on the person's mood who said it and the vast majority of the time, the reason it is said with contempt in their voice is because the other person is ignoring social norms and being rude themselves. Your example of standing in a crowded shop is quite apt here. The socially acceptable thing to do when you notice someone who wants to get by is to move back slightly and try to let them through. When you just stand there blocking the path without even trying even in a crowded shop, you have broken social norms which annoys people. It can also of course be also be used rudely when someone is in a rush and is frustrated that people aren't obeying social norms fast enough, but I find that to be far more rare.