"One of Our Dogs is Missing"-- the Robinsons find an Earth-dog on their planet, also a castaway from a space-voyage. The dog helps them drive away a powerful native monster, but the violence is only functional and is therefore subcombative. (SC)
"Attack of the Monster Plants"-- Dr. Smith causes some of the local flora to mutate wildly, so that the "monster plants" attack the ship. The crew destroys the plants with a chemical attack. (SC)
"Return from Outer Space"-- Will accidentally time-travels back to early 20th-century Earth, and eventually returns to the usual planet. (SC)
"The Keeper, Parts 1-2"-- An alien collector of rare animals shows up and shows interest in collecting Earth-people. In the first part, his weapon fends off laser-fire, but is temporarily incapacitated when its mechanism is broken by a stone from Will's slingshot. In the second part, the Keeper tries to blackmail the Robinsons into giving up two of their kids, but he changes his mind when exposed to their familial goodness. (SC)
"The Sky Pirate"-- a piratical alien, Captain Tucker, shows up. He poses no violent threat, but an alien blob-monster pursues him for his treasure. When the blob has what it wants, it departs without violence. (SC)
"Ghost in Space"-- an invisible alien, acting like a poltergeist, wreaks havoc upon the Robinsons. At the end he is either slain or driven off by the dawning of the sun. (SC)
"War of the Robots"-- a "robotoid," a robot capable of free choice, menaces the family and is overcome by the Robot in a climactic battle. (C)
"The Magic Mirror"-- Penny must escape from a strange world inside a mirror. (SC)
"The Challenge"-- Will engages in a series of contests with alien boy Quano. overseen by John Robinson and Quano's father, "The Leader." The Leader usurps the tests to challenge the professor, resulting in a duel with "volta swords," which John wins. The story ends with the alien father and son squaring off against a cave-monster. (NOTE: this was the first time actor Guy Williams got to do more sword-dueling a la his earlier character Zorro.) (C)
"The Space Trader"-- an alien trader tries to add Smith to his collection. The Robot cancels his contract and drives him and his pet monsters away with some sort of sonic attack. (C)
"His Majesty Smith"-- an alien race selects Smith to be their sacrificial king; they are defeated by deception rather than force of arms. (SC)
"The Space Croppers"-- a trio of aliens who look like refugees from "Tobacco Road" show up on the planet. They plant a deadly crop which the Robinsons must destroy with gas-bombs. (SC)
"All That Glitters"-- Smith acquires the Midas touch from an alien artifact. Faced with a space-cop who wants to repossess the artifact, Smith chases them away by threatening to "metallize" them. (SC)
"The Lost Civilization"-- When Will plays "Sleeping Beauty" with an alien child-princess, he also awakens her army, all devoted to galactic conquest. John Robinson and the Robot manage to stop the invasion force by clobbering their commander and his flunkies. (C)
"Follow the Leader"-- an alien warlord's spirit possesses the body of John Robinson. Though the possessed Robinson has one short fight with Major West, the spirit is only exorcised when Will declares his love for John and causes John to expel the evil from his body. (SC)
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I'll note that if the series had ended with this season, I probably would not deem it to be in the combative mode, any more than other Irwin Allen serials like "Voyage to the Bottom of the Sea" and "Land of the Giants."