No, not necessarily. Here's where I need to see some clarification. It just needs to make sense. Draco was a good example of someone who wasn't truly evil at the core. He was just a bully--unlike his dad. But Lucius was expecting leadership out of draco.
i'm okay with the fact that he isn't evil. and, if it makes some sort of logical sense, i'm okay with him having thoughts and goals that, on the surface, appear to be the exact opposite of what most people would expect. that keeps him from being dull. And that can be a good thing. So long as its done in a logical way, so long as it makes sense.
it might well be that adonis is honestly not evil but that part of why he wants to be a de might very well be that he is being pushed into that by his family--perhaps some high pressure from his father or mother or something. and, if that were the case, that might explain a lot of why he is mean to everyone else.
And, once you answer some of those things about him, you will find that it gives you a lot more understanding of his thinking, his feelings, and how he would most likely behave. that will help you when you write his posts in countless ways. the more you understand the deeper layers of your character, the better your posts will be.
i am not saying you have to change his goals. what i am saying is that if he is not evil but he wants a job that is held by evil people, he has to have a good reason for it. nobody ever does anything wthout a reason. figure out the reason and you'll unlock a lot of the question that, right now, feel hard for you to answer.
it has always helped me with my characters--lots and lots.
am i making it any more clear?