Nobody can name the best bank universally because it differs by country and changes constantly, but the pattern of what works for expats is consistent. In most countries the large international banking groups and the biggest domestic banks in major cities are your best bet for English-speaking staff, English online banking, and familiarity with foreign documents. Smaller regional banks may offer better rates but can be hard work without the local language.
What to actually compare: whether the app and statements are available in English, fees for incoming and outgoing international transfers, foreign card and ATM fees, minimum balance requirements, and how easily you can open the account with your current visa status. If your home bank has partnerships or a presence in your destination country, that sometimes smooths both the opening and cheap transfers.
The most reliable research method is asking in the expat community for your specific city, because branch-level experience varies wildly even within one bank.