My technical first OC was a roleplay character named Misty. She, and even her brother, Stalker, weren't actually anything special. Their characterization was flimsy and they did things that didn't make sense, but whatever. They were, of course, bad, but like them and most of my early characters, they existed for about a month then I never used them again after their relevant roleplay ended.
The character I want to talk about is a character I still have and cherish to this day: Lisa Adrean Adeptus. She began as a witch with wings, devil horns, and goofy cat ears, tail, and eyes. She was also a shapeshifter that couldn't control her powers at all. She'd turn into random things at random times to lead to totally random shenanigans. In my first roleplay with her, she was a sweet-hearted ditz, but by the second time I played her, she had done a complete face-heel turn. She became paranoid, cold, distrustful, developed a vitriolic wit, and eventually earned herself the MOST TRAGIC BACKSTORY EVER (that she still kind of has).
Her silly physical appearance and edginess aside, she wouldn't have been a "bad" character then if I had been better at writing the personality traits that I assigned her. Just like my first few OCs, I didn't always play her the way I described her and so she did stuff that made no sense, like kidnapping someone who tried to kill her, begging demon hunters to be allowed to adventure with them, and just trusting people that she really shouldn't be trusting. At some point down the road, her shapeshifting got limited to three forms: cat, crow, and giant monster cat. Her powers and appearance got explained not through witchcraft, but through her being a transdimensional half demon, half angel.
In short, the poor girl was a hot mess because I didn't know how to write.
But I got better. And so did she. Gone are the days of her edgy half-demon glory.