Acnologia

Despite being human, Acnologia can transform into a dragon, which is why he has two different appearances. In his human form, Acnologia does not have a left arm, as he lost it in a fight in Tartaros, against Igneel. His human form is his favorite, having the body of a muscular young man, long spiky blue hair, blue paint on his body (the same as when he transforms into a dragon), wears a black cape and a collar with dragon claws attached. . 400 years ago, Acnologia was a cruel, bloodthirsty and violent person. He killed any and all Dragons he could, ignoring the fact that many were his companions.

In the present, Acnologia is a recluse who wants nothing to do with humans, despite the fact that he is one of them. I think this form makes him more frightening, as he has a certain murderous look, oppressing the enemy, which ends up making him darker. We also know that he can transform into a dragon at any time. Hating humans, Acnologia is always alone, because due to his power being very high, he doesn't need anyone by his side, especially if he's a human, but he still doesn't like it. He had to spend a lot of time in his draconic form, but upon arriving at the Fairy Tail adventurers guild he recognized someone who caught his interest, causing him to kidnap her and make her his first companion. But after he kidnaps her, he slowly gives her the freedom to fight alongside her as a companion. he likes to tease arrogantly