Board Thread:Naruto Discussions/@comment-39172349-20190924183338/@comment-9782468-20190924204122

Shisui was noted by Danzo to be the most powerful Uchiha of his time. He was 16 when he died.

I'm going to assume he was at least as powerful as Itachi in Part 1 (when Itachi was 17), and Itachi was on par with people like Jiraiya at the time.

Shisui would most likely beat Danzo if they fought, he was only caught off guard by Izanagi.