What happens to a Three who lives for hundreds of years? Even success becomes boring eventually. He, Alina, and Mal are in a love triangle, plotwise and also in the Enneagram. Three to Six to Nine and around again. Strengths and weaknesses rebound back and forth. It’s all slightly inbred and squirmy.
He’s not only respected because his power is so overwhelming. He genuinely works to improve his Grisha army. Although his goal is basically world domination, he wants it for his team, not just for himself. It’s possible he cares for Alina as more than a tool. It’s hard to say; over the years he’s whittled away a lot of human frailty. What’s real and what are sales tactics with him isn’t always clear.
Again, Three. He’s fooled himself along with the rest of society. And the threat that he’ll take over all of civilization is not just a product of his evil power. He has the talent and personality of a Three that make his chance of success genuinely possible.