That's a really good question. At this point I've played a looooot of different characters, but if I had to pick some absolute favorites.
From RP the list is a bit shorter, a lot of RP characters I made were made when I was younger and I have less attachment to them now. Still, Jackson Crane will always be a stand out to me, from Z: A Kalos Journey. A rough and tough delinquent who had a troubled past, he became a pokémon trainer in order to support his "sister" (a girl named Malorie he had taken care of since they both lived in the same orphanage). Jackson had a really satisfying arc where he transitioned from someone who only cared about himself and his family, to someone who took on a big brother role amidst the PC's out of necessity and turned himself from a violent, angry jerk into a determined, rough around the edges protector who just wouldn't stay down.
From TTRPGs the list is a little longer, but the first character that comes to mind is Garen Heinrich Verschollen. A cleric engaged to a beautiful woman, his mother had been reviled by the town for dabbling in necromancy, despite only having noble intentions. When his younger brother picked up the torch to follow in their mother's footsteps, the church (including Garen's fiancé, yikes) had him killed. Garen begged his God to save his brother, but his prayers went unanswered and Garen abandoned his oath. Taking his mother and brothers notes, he became a necromancer, intent to prove that any magic (regardless of origin) could be used to do good and help people. He secretly harbored a wish to become powerful enough to resurrect his brother, without the help of the Gods. As Garen grew and got closer to the people around him, he found a family in the most unlikely of places with the other PC's and after returning to his home and liberating it from a mad man intent on destroying life as he knew it, he finally let go of his grief and said goodbye to his brother after many long years, accepting that one day he would die and see him again.
There are a lot more, including my most recent character, Aik, but I'll hold off on including them until I experience them and their arcs a little more haha.