On Axel/Xaldin day(there's some stuff on these two, but not much). For those who forgot, "headspace" simply means your own "take" on the character and how you see(or rather, want to) see them.
1. Axel's teardrop tattoes were "symbolic". Even if he lacked a heart, he still "felt", even though he was "incomplete". He got them soon after he lost his Heart.
2. Axel is a damned good cook. He specializes in chili and spicy sorts of food. Axel food is tasty food, but he almost always thinks only of himself when he does cook.
3. Axel's, er, "Other" grew up impoverished, but remained "nice"(harhar) until his parents died. He ended up homeless and made money through street performing until certain people noticed him, and they trained him to be an assassin. That's already been mentioned in previous posts. After he lost his Heart, he saw no reason to try "being good", so he ended up becoming far more evil than he ever was with a Heart. "The Devil himself", so to speak.
4. He was ambitious in the Organization. By appearance, it's "not his style" to want power, but Axel wanted it badly after spending years at the bottom. However, even with Demyx and Roxas, he found that he couldn't. Despite Axel's very powerful personality, he knew that he'd unable to command the level of loyalty Xemnas and Marluxia had, and he knew that he would never be able to. He resents the others for this.
5. Even without his secret ambition, Axel still had many mutual enemies in the Organization. They looked down on him, and he hated them for it. Despite that, he did get along with Xigbar, Xaldin and Luxord to an extent. With everyone else? Not so much. Oh, and Roxas doesn't count for obvious reasons. As for Demyx, well, he is a "special case". More on that later.