Which of the below sentences is more appealing?
He makes repeated efforts to overcome obstacles.
He makes repeated effort to overcome obstacles.
Which of the below sentences is more appealing?
He makes repeated efforts to overcome obstacles.
He makes repeated effort to overcome obstacles.
I think that, if it is repeated, then it should not remain singular. 'He makes repeated efforts,' therefore.
Or, 'he repeatedly makes an effort', would be good.
https://en.wiktionary.org/wiki/effort But, technically, it seems that the word 'effort' can mean either the energy exerted or the actual exertions themselves, so it appears that neither of the statements in the question is actually wrong, as such.