Which Tales of Character did you had the most fun fighting against?
Abyssion, hands down. Oh the countless hours that my friend, my sister, and I wasted trying to beat him because our characters were only in the 60-70s whenever we tried to face him. Some of the best moments of my life, I'd say. Sometimes my sister and I would be bored, and thus we would pick up the game, pick the file with Abyssion, and try to defeat him in all sorts of ways on different difficulties. It's so much fun!
Then it would have to be Yuan and Botta, solely because of the 1/2 EXP on Hard file that my sister and I tackled. See, we're not the greatest at video games so we spent oh about... three hours trying to beat him and Yuan? It wasn't aggravating though! Instead it was hilarious and amaaaazing, and we had a ton of fun doing it! Of course, then we cheated and brought the difficulty level down for the Dragon's Nest because we didn't want to waste more of our life trying to defeat another boss, one we thought was more difficult than Yuan and Botta.
I also have fun beating up Remiel, Kvar, Rodyle, and Mohs, because I hate them. I also like to try defeating Sync with one Guy, but it's a bother when I lose because of a certain cutscene you have to see before you face him (luckily you can actually skip that cutscene, derp). Fighting Mithos with one Presea has been fun as well, though I don't do it as often ever sense he peaked into my favorite antagonist and favorite Tales of Character in general spot. I've grown to be a bit sympathetic and thus I don't try when I face him. I also have a separate save spot for whenever I want to defeat the other God Generals (final battle with them) other than Dist (hurrhurr), but none of them were really used as often as Sync's (even though he's my favorite God General), and I think Arietta's have been used second.