Idk I wasn't that excited about Jack. Croc is good, I didn't really care for Lucci either. The Admirals I like as characters but not as villains, they're villains for a generic reason. Kaido has been pretty cool from what he's had but we don't even know if he'll be a real villain for Luffy.
Is an enemy and a villain the same thing in this case though? Bellamy was an enemy but he wasn't really a villain, he was just another pirate. Villains typically play a more nefarious role, Croc/Doffy taking over a country, Moriah taking his shadow, Hody tried to kill a king and queen. I see the Yonkou being enemies but not really villains to Luffy for one Shanks won't be a villain, Big Mom probably won't be either after learning of Lola. BB might be the only real villainous Yonkou, though Kaidou was working with Doffy so maybe he will be too.