It's a given that heroes will only become more impressive as the series goes on. They continue to face stronger and stronger enemies, which requires them to train or get better in combat. But that assumption isn't necessarily true for villains. They're not constantly getting into battles, and on the contrary, sometimes reach their incredible level of strength and don't fight anyone else.
If they're defeated by the hero, or easily defeat the hero, they still don't improve on their strength at all. And then later down the line, when they run into the protagonist or even other heroes, they find themselves surprised by how easily their formerly great strength is decimated.
10 Grand Fisher Went From Nearly Killing Ichigo To Being Taken Out In A Single Sword Strike (Bleach)
The Grand Fisher was originally a powerful Hollow that easily smacked Ichigo around. Ichigo did everything he could to fight back, and ultimately leaves the battle severely wounded.
However, the Grand Fisher makes a return in the second half of the series, having supposedly upgraded into becoming an Arrancar. But despite this so-called upgrade, Isshin Kurosaki is able to defeat him with a single swing of his sword.
9 Pegasus Was Easily Defeated By Kaiba In The Yu-Gi-Oh Movie Pyramid Of Light (Yu-Gi-Oh! Duel Monsters)
In the Yu-Gi-Oh! movie Pyramid of Light, Pegasus makes an appearance once again. Here, Kaiba believes Pegasus has a way to defeat all of Yugi’s Egyptian god cards and commands Pegasus to hand his deck over. However, Pegasus refuses to let them go without a duel.
Though Kaiba was crushed in their first match against one another, this didn’t seem to matter in the rematch. Kaiba had improved himself drastically, and without the Millennium Eye and having not changed his deck at all, Pegasus was easily defeated.
8 Piccolo Jr. Went From Goku's Biggest Rival To Becoming The Fourth Strongest Person In The Z Fighters (Dragon Ball Z)
Piccolo spent much of his time training to gain enough power to defeat Goku. Despite this, throughout the Saiyan Saga, he began to trail further and further behind.
When the two of them went up against Raditz, he was not much weaker than Goku, and Goku would have had trouble edging out a victory against him. But by the time Goku returns from training with King Kai, not only is Piccolo not even half as strong as Goku, but Goku has the Kaio-Ken to make it not even a slightly close match.
7 Broly Can't Even Beat Goten & Trunks By His Third Appearance (Dragon Ball Z)
Broly is probably one of the most notable victims of this. His first appearance automatically made him one of the most popular movie villains in the entire franchise.
In Broly’s first appearance, he beats up the entire cast, and ultimately they only beat him through a plot armor and the fact that the movie had to end at some point. But by his third appearance, he’s a weak clone that gets beat up by Goten and Trunks. People try not to even mention Bio-Broly.
6 Tarant Shank Goes From Legendary Space Pirate To Joke Of The Series (Tenchi Muyo GXP)
The main villain of Tenchi Muyo GXP, Tarant Shank, is a dangerous space pirate that kills most of the crew of Seina’s ship. He also nearly kills Seina as well, but fortunately, he manages to escape with the help of his friends.
With each subsequent appearance, he’s less and less impressive, and by the end, he’s showing up and getting taken out by a mecha that Seina barely even knows how to pilot.
5 The Dark Masters Are Defeated By The Digi-Destined Even Though They Never Get New Forms (Digimon Adventure)
The Dark Masters are the main bosses of the Digital World, and the ones who were behind most of the enemies the Digidestined had to fight for much of the series.
They’re a collection of Mega-Evolved Digimon, and watching the series and observing the trends up until that point, one might assume that the heroes would need to find an evolution beyond Mega to defeat them. But that’s not what happens, instead, the Digidestined just gain better control over their Ultimate and Mega forms and defeat them through experience.
4 Team Rocket Started As Serious Pokémon Thieves & Became A Running Gag. (Pokémon)
With pretty much every season, Team Rocket makes their appearance early on with some dangerous threats that make them into some impressive-seeming villains.
And every season their threats become less and less serious until they’ve devolved into a joke. Nowhere is this more clear than in the original series, where the catchphrase “Team Rocket’s blasting off again!” is first coined.
3 Mercenary Tao Goes From Beating Up Goku To Being One-Shot By Tien (Dragon Ball)
Mercenary Tao is perhaps one of the most embarrassing Dragon Ball fall-offs in the series. The character originally shows up and beats Goku, with him being so far above Goku’s level he’s able to hit him with his ponytail and take him out.
Tao makes several appearances after this and each time he becomes less and less impressive. Goku easily defeats him after training with Korin, but Tao makes another appearance in the last World Martial Arts tournament only to be defeated with ease by Tien. By the time he shows up in Dragon Ball Z, he’s pretty much just a comedy character.
2 Bluenote Stinger Went From Fighting Gildarts To Being Knocked Out By Natsu (Fairy Tail)
Bluenote Stinger was a villain that was one of the key members of Grimoire Heart. He was so powerful that he was able to smack around several members of Fairy Tail with ease, and it was only against Gildarts, their most powerful member, that he finally met his match and was defeated.
But eight years later, Bluenote hadn’t increased his power much at all. And matching up against Natsu again, not only was he defeated but he was taken out with a single attack.
1 Char Aznable Went From Being The Best Pilot On The Field To Being Destroyed By Amuro (Gundam)
Char Aznable is originally the most impressive pilot in Mobile Suit Gundam. He’s got the talent and a mobile suit specifically tuned to make him the fastest person on the field. The only problem is, he’s up against Amuro Ray. And while both of them are NewTypes, Amuro is a far more powerful one.
Char is gradually left in the dust as Amuro continues to improve. This improvement doesn’t stop at the end of Mobile Suit Gundam either, as by the time of Char’s Counterattack, he’s so much better at piloting that he easily defeats his life-long opponent.