So, title.
My character has been through a lot over the past 3 years (2018-2021), since that's when I started to RP in the first place. And throughout, he's been stagnating between hero or villain to put it into simpler terms, but as of recently for the past two to one years, he's been in hero. However, due to story and creative reasons, I've decided I want him to be an antagonist, or some type of criminal, through the Yakuza Syndicate since he is an eastern character and the Yakuza has been something related to his character due to family ties. Do note though, this is really my first time actually, truly, BEING an antagonist. And I've got to say, it's kind of hard. Hard may be an over-exaggeration, so perhaps challenging? I'm not sure how to really go about stuff in-game without making my character look like he doesn't know what he's talking about, because I, the player, also don't know what I'm talking about. Sure, I could chalk it up as my character learning how to be an effective criminal ICly, but I'm also trying to learn how to write an effective criminal without looking like I don't know anything at all.
Essentially, I'm asking every antagonist, villain, or criminal RP experts out there how can one, like myself, write and be an effective antagonist or criminal during roleplay?
Thanks.