Both of these fall to me under "refusing to exercise powers" rather than exercising powers though.
When the Queen dissolves parliament she's just going through the motions, it's a formality. If she had refused, say, Theresa May's request for a general election in 2017, saying that there was no need as the Government had a clear majority and Brexit needed to be the focus (and she did this by either hiding down the countryside, not answering her phone or by shooting down the idea preemptively) that would be a huge deal. That would be her exercising her power.
All of these former British territories are 1 terrorist attack and 1 ambitious politician away from a political crisis.
Roll the dice 10 times, each time one of these monarchs could make a play for power.
Although I'm not even sure how to handle the dissolution of the monarchy without executing everyone. Taking their property only means a foreign state would prop them up.
Usually such a role is a literal figurehead, or a de facto figurehead who de jure has power but culturally is not supposed to exercise them, (such as the aforementioned Queen, or the Irish President). Attempts by such a de facto figurehead to use powers they officially have have led to controversy, such as the 1975 incident with the Australian Governor General (https://en.wikipedia.org/wiki/1975_Australian_constitutional...)