Sten, Sebastian, Vivienne.
To be fair to Sten, I always sort of naturally ignored him in Origins. His unpleasant attitude never made me want to get to know him, and I eventually started passing over him at camp. Then at the end he thanked me for freeing him and said he wouldn't look for me on the battlefield and I was like... oh? We're friends? I feel bad about giving you the cold shoulder, bro. If I ever go back to Origins I'll give him a fair chance. I hope we run into him as Arishok in the future.
Sebastian was okay, but not someone I took out on missions often. And then at the end he LEFT me because of Anders? STAB YOUR FRIEND, OR I'M TAKING MY DOLLS AND GOING HOME. Granted, my Hawke didn't approve of Anders' actions at all despite being a mage himself. He felt betrayed, but didn't think taking a powerful mage off the board at that moment could help anyone. So he spared him for the moment, and Sebastian pissed off. And I was like, really? You're a DLC character, dude! I paid extra for you! And you want to demand things of me? You don't exist without my credit card! GOODBYE! And you can bet I denied that dork's request to invade Kirkwall in DA:I.
Vivienne, I just simply don't care for. I can sympathize with loyalist mages who prefer life in the Circle but to try and enforce that life on others who don't want it didn't fly with my Inquisitor. They remained civil but the two could have butted heads in an ugly way if allowed.