Just met the Arishok on my current run of DA2, and I instantly remembered why he's one of my favorite and imo one of the scariest characters in the series. Long rant ahead.
"You feed and feed and complain only when your meal is interrupted. You do not up look up, you do not see that the grass is bare, all you leave in your wake is misery. YOU are blind, I will make you see."
Besides the jokes made about his famous 'No' line and his boss fight, I find the Arishok so interesting and unnerving is because imo he feels so life like with his certainty that borders on the fanatic. Sten had a bit of this too, but the way the Arishok talks and acts is so intimidating because he is absolutely convinced that his way and the way of the Qun is the right way, and with his soldiers he has the means to enforce that vision.
There's no room for doubts or questions, no tolerance for dissenting opinions. His way is the only way, and he decides to 'correct Kirkwall of its faults'
To quote one of the characters of the game Wolfenstein The New Order: "I cannot believe with such certainty. For me, in everything, there must be doubt. Otherwise, there's no room to question, to learn.
This place. This is the fruit of unquestioned, ferocious conviction. This is where absolute certainty leads"
In the end, that's why I find the Arishok so interesting and scary. Cause his 'absolute certainty' feels very real, and when people have that 'absolute certainty' is when they are able to convince themselves that everything they do is right and for the greater good, as it has happened so many times in human history.
And that kind of thinking can lead down to very dark paths.