How to Disagree in English

source: Espresso English
(some essential expressions from the video)
# to express disagreement directly but politely: 
--I'm afraid I disagree.
--I beg to differ.
--I'm not so sure about that.
--Not necessarily.
--I don't see it that way.
--I'm sorry, but I don't agree.
--Yes, but ...
# indirect disagreement: 
--Well, in my opinion ...
--Actually, I think ...
# informal expressions: disagreeing [only between close friends]
--No way!
--You can't be serious.