William Strannix is an ex-CIA operative who specializes in taking down or taking over ships and submarines. When his superior, CIA Director Tom Breaker, believes Strannix to be going rogue, Strannix responds by murdering the men sent to kill him and, along with his crew, hijacks the battleship USS Missouri, killing several of its crew. Strannix coldly kills a random hostage just for standing next to another who got killed for trying to fight back and warns of doing the same again unless there's more cooperation. Strannix has a satellite station blown up along with both a fighter jet sent to check on the battleship and a helicopter with a rescue team, the latter two of which could lead to the whole ship being destroyed in an airstrike by other fighter jets. He amusedly lets the crew's lives be threatened in order to try to trap and kill ex-Navy SEAL turned cook Casey Ryback and fires two nuclear Tomahawk missiles towards Honolulu to kill everyone there.
Commander Krill is Missouri's Executive Officer who helps Strannix and his men infiltrate and take over the ship, just because the Captain believed (for good reason) he was too abusive towards the crew. Krill, having a bottomless hunger for power, personally murders the Captain, and before the hijacking, he drugs Playboy Playmate Jordan Tate, claiming that the pills he gave her are for motion sickness. From that point forward, Krill endorses and takes part in all of Strannix's plans and actions, including turning nuclear weapons on the ship over to allies on a North Korean submarine. He expresses gleeful sadism at Strannix's plan to bomb Honolulu with two Tomahawk missiles, and tries to lure Ryback into a trap where he can be killed. This involves Krill trying to drown the entire crew in the room they're being held in by having it flooded, and taunting Ryback about it over video while one of the hostages is shot and killed for good measure.
Admiral Bates is one, thanks to being a Reasonable Authority Figure who averts the stupid chief cliche of '80s and '90s action movies by authorising and supporting Ryback's effort to take back control of the USS Missouri. The filmmakers must have agreed, since he is the only other character to return for the sequel.
Ramirez, Ryback's assistant cook and one of his Ragtag Bunch of Misfits, is another likeable supporting character thanks to a charismatic performance from a young Raymond Cruz.
Tom Wood, the actor who plays Private Nash (who guards Ryback in the meat locker and neglects to take his pies out of the oven) would play Noah Newman in The Fugitive just one year later, again with Tommy Lee Jones. And later would reprise that role in U.S. Marshals.
Raymond Cruz, of Breaking Bad fame has several scenes as Ramirez, Ryback's assistant cook and one of the sailors who help him fight Strannix's men.
Squick: Ryback crushing Strannix's eye with his thumb, complete with oozing sludge.
What an Idiot!: The Masters of Evil have secured the mansion, have Jarvis and the Black Knight as helpless hostages, and banished Captain Marvel to a darkforce dimension. Now, thanks to Hercules' reckless Leeroy Jenkins act, they have beaten him to a pulp and almost killed him, and also defeated Captain America and the Wasp. You'd expect: They would keep all the defeated Avengers as their hostages (those listed were the whole regular team at the time), keep a low profile, and torture and kill them at their leisure. Nobody would know anything until it's too late. Instead: They let the Wasp leave, get rid of Hercules' body (who is then saved at a hospital, as he was actually Not Quite Dead), and surround the mansion with darkforce. A giant banner saying "overrun by villains" would have served just as fine. The Wasp manages to get enough reinforcements, and starts the counter-attack.