Which of these languages...

is the most worth learning, in your opinion, and why?

Russian, Turkish, Urdu, Punjabi, Korean, Hindi, Arabic, Chinese, Bengali.

Additionally, which countries that speak these languages are pleasant and which are shitty?

Out of your list my order would be Russian, chinese, turkish, korean & hindi. Urdu, bengali are useless since only a certain state speaks it, urdu is almost hindi also. As a native indiafag dont bother learning an indian language since most indians that you will interact with will speak basic english even though its with a heavy ass accent. So learn either russian or chinese with turkish and korean on the latter end.

Currently speak english, hindi, telugu. Learning swedish at the moment. Hopefully I will be able to learn russian, italian & japanese before I die.