I’m not generally a fan of mechanized villains. For the most part, they seem like an easy device to turn excessive violence into bloodless mayhem. An example would be the battle droids in Star Wars. Mow hundreds of them down and still receive a PG rating. It’s the same with Megatron in Transformers.
There have been some terrific machine villains: machines that were scary, clever, and tough as tempered steel. The irony is that all of the great bad-guy-machines were humanized—which meant they couldn’t be indiscriminately killed by the dozens. My favorite is Roy Batty, the leader of renegade replicants in Blade Runner. Batty was humanized to the extent that he cried, found redemption, and bid our hero a great life.
Spielberg invented a vile machine in Duel, his first full-length movie. The rusted-out semi chased our common-man hero over hill and dale. Granted, there must have been a driver, but we never saw him and the truck itself was portrayed as malevolent. Christine was another wheeled vehicle that seemed more human-like than some of the cast. The Terminator is an obvious example, but the T-800 stayed a mindless robot for the entire first story. It wasn’t until Arnold Schwarzenegger went over to the light-side that later incarnations were humanized. West World’s gunslinger, Gort in The Day the Earth Stood Still, and HAL in 2001: A Space Odyssey are other great examples.
Machines can make great villains, but if you want the audience to care if they are defeated, then you need to give them a personality.