Diamond Tiara is my favorite pony and has been for a very long time. For a short while after I started watching, it was Sweetie Belle, but that soon changed and hasn't since, though SB is still second. At first I sympathized with her because of some of the ridiculously vitriolic comments I saw directed towards her, asking for torture, death or worse, when she was still an antagonist. But with Ponyville Confidential (my favorite ep), I saw something more in her that I loved. She was determined to succeed in her role, and was willing to do anything to achieve it. Now, maybe the blackmail was too far, but to be fair, the CMC came up with a popular idea and then tried to back out, which would've hurt DT and her paper so I didn't blame her too much. Then the episode tried to place all the blame on her and I was even more sympathetic. Later came Flight to the Finish (and more sympathy-garnering hate towards her), and Twilight Time (Which further cemented her as a more complex pony than given credit for in my eyes). And of course COTLM proved she was an awesome pony. I've been fully on Team DT is Best Pony for a long time and am not getting off. There are other reasons that I sympathized and identified with her as a villain which I'd rather not discuss.