"Gotta hand it to you, though. Pretty ballsy comin' after us all asymmetrical like that. But four hands are better than one... Long story short, you're gonna die."
Future Android 17 (未来の人造人間17号, Mirai no Jinzōningen Jū Nana-Gō) (Future Cyborg 17) is the alternate timeline counterpart of Android 17 and is first seen in the special "The History of Trunks". Unlike his present counterpart, this version is extremely evil and more sociopathic, doing nothing but killing innocent people and causing massive destruction.
In the Anime
In the anime, unlike his main timeline self, Future Android 17, alongside his sister, is extremely sociopathic and cruel, taking joy in killing and destruction. According to them, the two sibling androids' personalities is the direct result of Dr. Gero's attempts at programming them to hate humans as part of his bid to conquer the world.
In Dragon Ball Z Abridged
In Dragon Ball Z Abridged, Future Android 17 acts exactly the same was he does in the anime, being completely evil (possibly more than his sister) and takes it upon himself killing thousands of innocent people and causing massive destruction. Similar to his main timeline self in the abridged version, he seems to not be self-secure as he dyed his hair black in order to not be confused with his sister (despite both of them having different hairstyles and skin tones). At one point in the movie, he does show some boredom of destroying things and at one point decided to stop being a killing machine and become a park ranger (which can be considered a mythology gag as he becomes a park ranger by after the Cell Saga in the original Dragon Ball Z), but eventually decided against it after getting kicked into a building by Future Gohan.
The androids make their appearance six months after the death of Goku by murdering all of the Z-Fighters one by one, leaving the world with very little hope. Thirteen years later, the androids still continue to cause havoc across the Earth by destroying small town after small town, working their way up in destroying larger populations. While destroying Paprikaburg, Android 17 is seen recklessly driving a hovercar, running over various innocent people in the process, and asks his sister if she was keeping score, who was currently irritated at him for destroying a women's clothing store earlier that she liked. By the time Trunks (Bulma and Vegeta's son who was a baby around their reign of terror thirteen years ago) arrives, the entire city has been reduced to nothing, with the androids nowhere to be seen.
The next day, the androids attacks SuperWorld while having fun with all of the rides. However, their fun was cut short by the arrival of Gohan (the only surviving Z-Fighter from thirteen years ago) and Trunks, with Gohan challenging the androids to a fight. As a Super Saiyan, Gohan seems to be gaining the upper hand against 17 until 18 joins the battle and overwhelm the Super Saiyan in a two-on-one battle. This causes Trunks to rush in to help Gohan, but he gets easily overpowered by Android 18. Before 18 can deliver the finishing blow, Gohan manages to catch her off-guard and proceeds to hide inside the ruins of the theme park. After failing to find the two Saiyan hybrids due to the inability of sensing life energy, the androids decide to bomb the whole area with "Scorched Earth", which causes Gohan to lose his left arm as a result.
Later while destroying another city, Android 17 announces that he is bored of destroying things and plans on becoming a park ranger before gets kicked into a building by Gohan. While this only leaves Android 17 in tattered clothing, this does manege to irritate him as he decides to kill every human on the planet before "ranging the shit out of that park". After taunting Gohan by making a couple of hand-puns, the androids easily overpower Gohan and murders him by shooting down a barrage of ki blasts from he sky. However, this event does cause Trunks to finally become a Super Saiyan due to the grief and anger of losing his mentor and best friend.
Three years later, the androids are attacking Cuminopolis before Trunks, now in his Super Saiyan form, arrives and challenges the androids to a fight. While it first looks like everything is going well for Trunks, the androids quickly turn the tide of the battle and easily overwhelms him. After beating him down to the point where he reverts back into his normal form, the androids recognizes Trunks as the person they encountered at SuperWorld three years ago along with Gohan. As 17 prepares to finish him off with a large blast, 18 suddenly gets in front of him at the last second, causing him to accidentally blast her at point-blank range. This infuriates 18 as she proceeds to leave the city as 17 tries calm her down, leaving Trunks behind and surviving his foolish assault on the androids.
Later, in Parsley Town, 17 is seen with 18, who is destroying some buildings out of anger after someone called her a "hoebot". When an old man shot at him with his gun, to no avail, 17 approached him, shooting and killing him with his own gun. Future Trunks then arrives at the scene, declaring that he and his sister's lives end now and that nobody else is going to die (even though 17 already killed someone before he came in). 17 is surprised that Trunks is still alive and kicking after their encounter, and is even more surprised when he came in without his sword and his jacket, and how is he has gotten jacked. After Trunks makes short work of 18, 17 asks if he can talk it out with him so he can have his life spared. Trunks then asks 17 a question about Future Gohan's name, the man he and 18 killed. 17 incorrectly answers if his name was "Goku Jr.", so he is promptly kicked to the ground and is destroyed with a Ki blast from Trunks.
- Just like his present self, Future Lapis said he wants to be a park ranger, however he's too evil to care about Future Gohan let alone animals
Android 17: Hey, 18! You keepin’ score?
Android 18: Why would I be doing that?
Android 17: *sighs* You said you would!
Android 18: No, you said, "Hey, check this shit out!", then jumped in a car.
Android 17: Aw, come on, sis. Is this about the shop earlier?
(flashback of Android 18 exiting a clothing store)
Android 18: Oh, man, you wouldn't believe this haul. This is why I love these little inner-city shops, they always have the best brands... (Android 17 destroys the store) What the hell?! Why did you blow it up?! They were giving me free clothes!
Android 17: Didn't give me nothin'.
Android 18: It was a woman's clothing store!
Android 17: Hey, I'm perfectly secure.
Android 18: Is that why you dye your hair?
Android 17: Tch, don't hate. -- "The History of Trunks"
Android 17: You know what? I'm bored.
Android 18: Well, we could find another city?
Android 17: No, I mean, like... bored of this whole "great destroyer" schtick, you know? Destroying things, killing people... (fires another blast) It's just boring.
Android 18: Yeah, it's kind of lost its luster. After you wipe an entire genre of music off the face of the Earth, what's left?
Android 17: You know what I always wanted to do? Like, since before all this? ..Be a park ranger.
Android 18: You wanna range a park? (sends another blast into the distance)
Android 17: Hell, yeah! Livin' outdoors, communicatin' with nature, shootin' poachers... Yeah, I think I'ma do tha-- (gets kicked through a building by Gohan) You goddamn cheatin' son of a bitch!
Android 18: *laughs* He slapped your shit!
Android 17: (with his clothes all ruffled up) Okay, you know what? That’s it! I'm killin' every human! EVERY. ONE. Then I’m gonna range the shit out of that park. -- "The History of Trunks"