Nearly every one of Goku's friends started off as a major antagonist at some point before becoming one of his most trusted confidants. When he and Yamcha first met, Yamcha was focused on stealing all of Goku's possessions, while Vegeta and Piccolo wanted nothing more than to destroy the very planet he called home. Android 18 had been programmed to kill Goku, but after his death at the hands of Cell, she managed to settle down into domestic life with Krillin, but even though she's managed to become one of Earth's strongest defenders, this still doesn't excuse her of the terrible things she's done both in Dragon Ball Z and Dragon Ball Super.
10 Joked to Trunks About Her "Future" Death
When Trunks returned from the future to seek help dealing with Goku Black, he was shocked to see just how much the past differed from his own time. After meeting up with Krillin, he was at a loss for words when he discovered that he and Android 18 were not only married, but had a daughter together. Despite being aware of the mental trauma that Trunks carried with him after living in a world ravaged by 18's future counterpart, she joked that Trunks owed her for killing her in his timeline. Though no actual harm came from this, she could've come up with a hundred other jokes to say to a man who literally had nightmares about her for most of his life.
9 Extorted Mr. Satan
At the 25th World Martial Arts Tournament, Android 18 found herself fighting Mr. Satan in the finals. Instead of just defeating him, she agreed to let Mr. Satan have the victory if he paid her double the prize money. Though it was admirable that she let him keep his fame, blackmailing someone so much weaker than her is pretty much bullying. In the Dragon Ball Z film Bio-Broly, it is revealed that Mr. Satan didn't hold up on his end of the deal, prompting Android 18 to fly to his home and begin to tear up his house. She allowed her villainous side to get the best of her, and could've easily waited until Mr. Satan gathered the money. We're not saying that Mr. Satan doesn't deserve something like this. We're just saying Android 18 didn't have to be the one to do it to him.
8 Ignored Gohan's Plan During the Tournament of Power
Before the Tournament of Power, Gohan came up with a safe plan: Universe 7 would fight together, only splitting up to outnumber their opponents during fights. Of course, with Frieza, Goku, and Vegeta on the team, all warriors who enjoy doing things solo, we all knew that his plan was foiled from the start. What we didn't expect was for Android 18, and even 17 for that matter, to ignore Gohan's plan as well, especially since she and her brother are strongest when they fight as a duo! In the end, Universe 7 won regardless, and the warriors were bound to get separated at some point, but 18 abandoning the plan in the very beginning didn't do a thing to increase an already wavering team morale.
7 Took Krillin's Money
When Krillin married Android 18, he also married the perfect training partner. Though she might be stronger than Krillin, he could at least keep up with someone who wasn't from another planet. The two were shown in Dragon Ball Z preparing for the World Martial Arts Tournament together, and Krillin's reflexes seemed to improve as a result. In Dragon Ball Super, Krillin and Android 18 were shown sparring, and she easily knocked him down, refusing to hold back. Instead of apologizing, she gloated and claimed that his 10 million Zeni was hers. This is hardly better than what she did to Hercule, except this is just a bit worse since she extorted her own husband on a bet he had no chance of winning.
6 Insulted Krillin Right in Front of His Daughter
Dragon Ball Super didn't do Krillin any favors. Gone was the brave martial artist who would charge at enemies he knew he couldn't beat. Super left us with an even shorter, more cowardly version of Android 18's husband who constantly doubted himself. After Krillin got himself injured during a robbery, Android 18 called him out, claiming that this timid version of Krillin wasn't the man she fell in love with. Although Krillin needed this kick in the pants, it was cruel to insult him in front of his best friend and his daughter. To add insult to injury, Marron began to compare Goku and Krillin, and claimed that she wanted a father who was strong. For someone who couldn't even complete the one task they were programmed to do, Android 18 sure does talk a big game.
5 Scolded Krillin For Losing to Frost
No matter how hard Krillin trains, there will always be a limit to his abilities. That's why when Frost knocked him off of the arena, we weren't too surprised. Sure, it wouldn't have happened if Krillin wasn't too busy celebrating his win against Universe 4's Shosa, but at the same time, Frost was just a superior opponent. After he was sent to the stands, Android 18 berated him, making it known to everyone that she was ashamed to call him her husband. What makes this worse than the previous entry was that she merely joined in with everyone else who insulted Krillin, instead of defending her husband, especially since he had just saved her from being the first Universe 7 fighter to be eliminated.
4 Broke Vegeta's Arm and Trunks's Sword
As if breaking Vegeta's arm wasn't vile enough, she also managed to break Trunks's sword just by blocking. Not only did she cripple Vegeta's pride after giving him one of the series's most brutal beatdowns, but she also shattered Trunks's most prized weapon, rendering him swordless for the rest of Dragon Ball Z. Although it was never been confirmed in the series, the Dragon Ball Z film Wrath of the Dragon alludes to the fact that Future Trunks got this sword from Tapion, who he considered as a brother, although Future Trunks's own timeline complicates this possibility. Regardless, it's safe to assume that this sword has huge sentimental value to him, and Android 18 broke it, along with Vegeta's arm, without a hint of remorse.
3 Robbed A Boutique
As one of the most stylish characters in Dragon Ball Z, one of the first things Android 18 wanted to do after she dealt with Vegeta was to get some new clothes. Of course, she had no intention of paying, and after she walked out of the store in her brand new, discounted outfit, the cops were right on the Androids' tail. In seconds, Android 18 dealt with the cops, punching through one car and causing it to combust, while flipping the other two completely over with just her arms. The poor cops didn't stand a chance, and Android 18 definitely killed some of the officers in the violent incident. Given that 17 or 16 never killed cops over something as mundane as clothes, Android 18 cemented her place as the cruelest of the trio.
2 Tricked Vegeta Into Killing Innocent Civilians
During her fight with Vegeta, we noticed that these two were nearly equals in terms of raw power. What eventually led to Vegeta's defeat was the fact that unlike Android 18, he wasn't blessed with infinite energy at his disposal. Looking to toy with Vegeta, 18 only evaded his attacks for the first few moments of the fight, and Vegeta's recklessness caused him to kill several drivers, a few sheep, and their herder. Android 18 saw the evil still within Vegeta, and exploited it for her own amusement, while also making the Saiyan prince expend his own energy. What's worse is that after Cell was defeated, the wish made to bring back everyone killed by his hands wouldn't have applied to these people, who'd all been killed by Vegeta. Still, at the end of the day, Android 18 has blood on her hands as well.
1 Murdered Millions of People in an Alternate Timeline
Of course, the worst thing Android 18 has ever done belongs to an alternate version of herself. Though this isn't the 18 we all know and love, she is wholly capable of this, and she would've murdered Gohan, Tien, Krillin, Vegeta, Piccolo, and countless other innocent humans if Trunks hadn't intervened. There aren't many villains in the entirety of the series who could coldheartedly murder millions, but what made Android 18 and her brother especially terrifying was the fact that they not only killed for fun, but they avoided exterminating Earth's entire population all at once so that they'd always have people to kill for amusement over the course of several years. In Trunks's timeline, 18 saw the destruction that she caused as a mere game, unlike villains like Zamasu and Goku Black, who killed people as a result of a strict moral stance. Killing for fun was what initially made Android 18 unforgivable, but at least she became a better person in the end.