I have to disagree with the advice to seperate him and get him some girls. You would be opening a whole other can of worms unless you are able to keep them very far apart. Putting females into the mix could cause all of your drakes to start fighting, again, unless you are able to keep them far apart. You could try seperating them into pairs and see if that works. Your best option may be to rehome him. If that is what you decide, be honest about his behavior to whoever takes him. It would be unfair to a new owner to "discover" he has a mean streak.
Good luck in whatever you decide.
Good luck in whatever you decide.