First of all, it's overall a very good drawing. The proportions are correct, lines are confident, there is a nice amount of detail, while it stills remains readable. Of course, there is always a room for improvement. Here's what I think could be better, feel free to disagree:
Artistically:
First - depending on a purpose of this drawing, it could benefit from a more dynamic pose. The one presented is kinda boring, which is fine if the drawing is supposed to just present a design, but less fine if it's supposed to be a standalone work. Second - it could definitely use more shading, right now, it's very flat.
Thematically:
I'm not the biggest DMC nerd, so I may be wrong, but there are two things I find questionable. First - it doesn't clearly convey whose DT it is. I thought it's Dante (because of the red dots, which in my opinion are not the best idea), Steve apparently thought it's Vergil? If I'm correct, apart from DMC1, all DT were very clearly red/blue, to fit the character. I think brown is too neuter. Unless that's what you were going for, but in this case, it requires explanation. Second - I'm not sure about the reptile face. I think DT's heads are usually rather antropomorphic. Of course you can make it whatever you want, but I feel like reptiles are a little cliche, and don't fit well with how devil triggers usually look like.
Oh, and also, I'd make his crotch bigger, it looks like he's been castrated