I am writing a paper. There is a term used in my work that represents "the degree of completion", i.e., 32% in the phrase "32% was completed". I tried "progress" but think it's not intuitive and "completeness" but find this should be used to represent if an event is complete. This term is important for my work hence I want to find a single and intuitive word to represent its meaning, any suggestion?
"Completion" itself works for what you need, see for example:
Any phrase composed of "(fraction/percent) completion" will be understood to mean the degree of completion.
In the example sentence you provided it would be simply:
"Our model can predict 30% completion of action for video frame according to the image content in that frame"
though the rest of that sentence could use some editing and I'm not sure what exactly you intend to convey.