Destroyermen/YMMV

Complete Monster: The Grik. All of them.
- That racist asshole who raped a 'Cat in book two. Walker's the enlisted men justifiably lynch him for it.
High Octane Nightmare Fuel: At the climax of book one, Matt and his crew team up with the Lemurians to board a Grik ship. The battle is horrific enough (though not without several badass exploits from humans and Lemurians alike), but then everyone glows belowdecks, to find a "brig" where Lemurian captives are being butchered alive for food, and the survivors are Forced to Watch. Oh, and this comes immediately after a human skull is discovered on the ship. That the Grik were keeping as a trophy.
Magnificent Bastard: Again, Silva. He has a habit of dealing out a ridiculously appropriate (and often over the top) lesson and/or punishment to anyone he thinks needs one. For example: one sailor is mocking the coxswain who has become terrified of the sea since arriving in the new world (for very good reason, and the coxswain continues to do his job despite being humiliated by his own fear). Silva's response? To pull the pin on the chain the mocking sailor was leaning against, leaving him to go tumbling over the side and only save himself by grabbing the chain. Afterward, he's afraid of the water.
- Let's not forget his "prank" on Chack (a Lemurian who joins the Americans on Walker): Silva proclaims Chack's sister to be his wife...and she goes along with it! Poor Chack was this close to murdering Silva when that happened.