What is the worst bank in Poland that I should avoid
Not sure which ones to avoid. The selection is decent...
But Alior is one that I personally do not like for some odd reason - probably their hopeless adverts...
ING is great for that actually - they offer free accounts in foreign currencies and free transfers between ING accounts. Combine that with a free service like walutomat.pl and you'll be getting the best exchange rates and transfers between your accounts.
PKO BP charge for everything, but omnipresent and has a good app. Getin Bank was also OK some time ago offering some money back each month, high rates, and with a nice app - probably the most Polish (in terms of capital) of all banks in Poland.
But all depends what you will need the account for - no one size fits all, I am afraid.