I recently watched his performance in Split and he was quite amazing. At times this split personality disorder characters seems annoying, but McAvoy does a great job.
His performances in X-men as well were commendable along with The last king of Scotland.
I won't name actors(cuz this is the limit of free speech on this sub, otherwise u r downvoted) , but there are some who are among brilliant actors but lacks that ability to engage audience on the screen (that charmness,if that's a word)