In Vol. 3 the menace is provided by The Green Goblin, Doc Octopus and Tombstone.
The Zeta Project: The First Season contains the two episodes of “Batman Beyond” that introduced its characters as well as the 12 first-season episodes. It’s about an android assassin who goes rogue with a teen accomplice when he realizes one of his targets was innocent.
Barney Miller’s third season was the one that added Steve Landesberg as a regular. His character, Arthur Dietrich, followed an Ignatowski-like arc, starting as one-shot guest character in season two. I consider the Dietrich years the show’s golden era.