Android 17 is one of the most notable characters to appear in Dragon Ball Z, even though he shows up in the next-to-last saga and technically starts as a villain. I also like that in the Funimation dub he’s voiced by Chuck Huber, who used essentially the same voice for Hiei in Yu Yu Hakusho.
Apparently, he and his sister were originally named Lapis and Lazul, but I don’t think the anime made that very clear. When they were first awakened, we assumed they were just mechanical androids, not cybernetically enhanced (human) cyborgs.
Just like in Future Trunks’ timeline, he immediately kills Dr. Gero upon being released. Dr. Gero had turned himself into an android, and he still got completely destroyed. That’s rough.
After that, he and Android 18 just kind of wander around figuring out what to do instead of carrying out the full-scale annihilation they caused in the future timeline. It seems they agree with Android 16 that the most fun thing to do would be to find Goku so they can fight and kill him. That’s a little odd, though, because they weren’t programmed to despise Goku the way Android 16 was. It raises the question: why kill your creator, yet still follow through on his ultimate plan?
Piccolo then makes the questionable decision to fight them after fusing with Kami, which makes him roughly an even match for Android 17. He hopes that by destroying 17, he can prevent Cell from reaching perfection instead of trying to form an alliance with them. Ironically, Piccolo was the reason Cell is able to track them down in the first place, since Piccolo has a detectable energy signature while the androids do not.
When it looks like Cell might be killed by Android 16, Android 17 suddenly loses all common sense and hangs around just to watch the fight, even though he knows he could be absorbed. He gets snatched up pretty easily, and I assume he technically dies when Cell is destroyed. Still, he’s one of the people wished back with the Dragon Balls afterward.
He’s almost entirely absent during the Majin Buu saga. If I remember correctly, he’s off protecting a forest and its wildlife or something like that. Interestingly, that idea gets expanded on later in Dragon Ball Super.