I love Thrawn from the Legends-Thrawn-trilogy. He's ruthless and cold yet also shows to care for his crew. He's dangerous and brilliant, and yet, also flawed, makes mistakes, loses more than one battle, shows a bit pride now and then. I love his dynamics with Pellaeon as well. These two were a great duo. Although I tend to side with the good guys, Thrawn (when reading this trilogy) managed to capture my fascination enough that I almost wanted him to win.
However, I was underwhelmed when reading Outbound Flight. I personally didn't like his version in that novel a lot; he was far less interesting in this novel than in his original trilogy and way too much of a do-gooder for my taste. All in all, I found him more shallow, less complex in this novel.
So, when it comes to his Legends version, I really like his portrayal in the original Thrawn-trilogy specifically