Crimson is a menace, and people like him that way.
Ragna Crimson introduces a very interesting character named Crimson. Crimson is a dragon, but he can be whatever he likes, man or woman. In the latest episode he was a man, so we shall refer to him as such.
Major spoilers ahead!
Crimson is an absolute menace, and his moral alignment is unclear, but he is often unhinged, which is shown very extensively through his design. We are not talking about the red-and-black outfit or a witch hat, which probably also contributes to the aesthetic. We are mostly talking about his mouth and eye.
You see, Crimson is good at pretending to be a normal person, and when he does that, only his green eye is showing, and his mouth is just a regular one. He seems to have lipstick on his lips, so the mouth is red, but it is normal-sized. However, Crimson does not always pretend to be normal. Sometimes he goes into the unhinged mode, and the further he goes, the weirder his face becomes. For one, his red eye begins to show, and for another, his mouth becomes unnaturally large, very red, and strangely shaped.
For example, in Episode 3, Crimson convinces Ragna to talk about Leo to "understand" him better, and he does it by pretending to be normal. When Ragna admits that he is terrified that something might happen to Leo, Crimson stops pretending. Immediately his mouth becomes bigger, but as he launches into an explanation of what Ragna should do to keep Leo safe, his features become completely distorted.
Crimson's Quick Shifts from Calm to Crazy
That plan of Crimson, by the way, involves kidnapping Leo and leaving her in one of Crimson's storage rooms drugged so that she cannot do anything but sleep. Crimson even suggests that it would allow Ragna to take care of Leo, which is something he had always enjoyed.
As Crimson talks about that, his entire face becomes distorted, and he sounds unhinged, but he quickly returns to somewhat normal as Ragna tries to hit him in the face for his plan.
Crimson also seems to switch between normal, unhinged, and angry very easily. Right after telling Ragna about his plan and evading a punch, Crimson kicks Ragna, who cannot move because of him overworking his muscles.
Crimson is a menace, basically, or a bastard if you prefer. His view of humanity is low, and he hates dragons, too. Watching him, however, is a delight, and we are looking forward to more unhinged behavior from him.