Okay so quick note, while I have listed his accent as 'North American', I am sorta specific on the kind of accent done. Personally, I have always seen Buck with a New-Yorker/Boston-y accent. I do actually have a very specific example, but I'll only provide that if any of you want (just pm me if you want the example and all). If you want to try your own thing, I don't mind at all, honestly performance matters more for this kind of character.

So Buck is a weapons developer and businessman. He is one of the three main villains but is the most prominent one in The Rig. Buck is talkative, eccentric, sadistic, manipulative and bitter, living behind 2 masks. His public face is often displayed as kind and gentle, great with people and a beautiful passion to help humanity as best as he can. Underneath it all, he houses a very dark heart full of hatred, anguish and sadness that wants to destroy the UNSC for wrongs they have done to him in the past. He works with an ambitious scientist in order for him to gain tech to take them down from the inside while also supplying her with money and some tech he creates on the side.

A great example of his personality is someone like Felix or Temple from Red vs. Blue