Captain America villain Crossbones would be The Dragon to the Red Skull's Big Bad. The merc Crossbones is a deadly physical threat, a skilled fighter and carries out the fisticuffs for the weaker(most of the time) but cunning Skull.
His daughter has acted as the Dragon on occasion as well.
The Batman villain Ra's Al-Ghul is usually accompanied by an extremely large thug named Ubu. Apparently this is a title, rather than a name; he tends to replace Ubus fairly frequently. Ubu was absent from the film, but Ken Watanabe's fake Ra's could be said to fulfill this function.
In the limited Superman, Batman and Wonder Woman series Trinity (the three issue Matt Wagner one, not the more recent 52 issue maxiseries), Ubu is present, but the role of Ra's Dragon falls to Bizarro, and the mysterious Amazon Artemis of Bana-Mighdall
In Ultimate Spider-Man, Elektra serves as the Dragon to the Kingpin of Crime. Not that the Kingpin isn't capable of quality violence in his own right...
In the same universe, the Ultimate X-Men'' have to deal with the Weapon X project, led by a human military officer named John Wraith. He isn't particularly tough, but his personal Dragon is the gigantic mutant killing machine Sabretooth.
In most appearances, Kalibak is The Dragon to Darkseid. If he could turn his other son Orion, Darkseid would make himThe Dragon in a heartbeat.
In the second adventure The Mystery of the Great Pyramid, Olrik gets his own dragon: Sharkey.
Sinestro becomes the Anti-Monitor's Dragon in exchange for an army that can rival the Green Lantern Corps. Sinestro, in turn, leads the army with the monstrous Arkillo as his Dragon.
In Bone, both Kingdok and The Hooded One have claims to the Dragon position. It could even be argued that Kingdok was the Dragon for the Hooded One.
In Star Wars: Legacy, Darth Krayt has many elite minions who act in the enforcer role, but the one who is closest to him and who he relies on completely is Darth Wyyrlok. In addition to being the only being in the galaxy Krayt can be said to really trust, Wyyrlok is also potentially more powerful than his master, as Krayt has been weakened by Yuuzhan Vong parasites. Ultimately, Wyyrlok subverts this trope in an interesting way- he remains absolutely devoted to Krayt's vision of a galaxy united under the Sith, but kills the Dark Lord anyway because he believes his master has gone insane and lost track of his true goals.
In Avengers Under Siege, Baron Zemo used brainwashing to turn the monstrously powerful (but mentally unstable) Blackout into his loyal Dragon. Blackout is interesting in that he defended Zemo from heroes and villains alike: he disabled the Avengers' most powerful member, Captain Marvel, and also prevented dissent among Zemo's Masters of Evil. Tellingly, Moonstone, in her role as The Starscream, spent the entire arc trying to win over Blackout rather than trying to kill Zemo.
Qztr and all the other Lawbringers are Charon's Dragons in Negation. Immensely powerful and willing to kill without mercy at Charon's command, they also (Qztr does, at least) act as a court of final appeals within the empire.
Norman Osborn of Spider-Man fame has had several Dragons over the past few years. When he formed the Sinister Twelve, Venom served as his Dragon. When Osborn became head of the Thunderbolts, he brought Venom along for the ride, but would also use Bullseye as his Dragon for more subtle work. Finally, when he formed the Dark Avengers, Venom and Bullseye stuck around, but Osborn now used the Sentry as his Dragon in most cases.
Sin City villains are often bad guys. Manute, Kevin, Blue Eyes, and even the Yellow Bastard to a certain extent are all dragons while the BigBads like the Roark family and Wallenquist usually work behind the scenes... and thus, a little more likely to survive the story.
In Earth 2, Fury, the last amazon, is Steppenwolf's right hand woman.