The biggest blunders made by a protagonist in animation.

[Antiyonder]

Simple rule of life. No one is perfect. People make mistakes, including those who have the role of the hero/heroes. The ones that stand out to me for the moment:

1. All versions of Spider-Man: Granted this is during his short lived stinct as an entertainer, he makes the decision to let a burglar run past him (most versions because he is indifferent whereas Spectacular he does it to get even with the fight promoter for cheating him out of money). As a result, his Uncle Ben is gunned by the same guy.

2. The Legend of Zelda "The Moblins Are Revolting": Long story short. Ganon is trapped in an energy bubble. A bubble that only the Triforce of Power can destroy. So Link, being the goofball portrayed by the cartoon, tosses Ganon around like a ball and nearby the Triforce.

And yet, Zelda chooses not to fire him or lock him in the dungeon. Go figure.

3. The Real Ghostbusters "X-Mas Marks the Spot": The Ghostbusters remedy this one, but still messed up in the first place regardless. The episode begins with them on a drive only for a timewarp to old England. During their time there, they successfully bust three ghosts. The ghosts who are suppose to rehabilitate Ebeneezer Scrooge, unfortunately.

As a result, Christmas through time is rejected by society thanks to Scrooge's book "A Christmas Humbug". Needless to say, Egon is successful in retrieving the 3 Ghosts, and Christmas is restored, but way to mess up guys.

[creativerealms]

Omi in the series Finale of Xiaolin Showdown. His plan to make Chase Young a good guy had a huge flaw that screwed everything up. It consisted of him freezing himself for eighty years to retrieve the sands of time that his older self hid. However because he Froze himself he created a time paradox and older Omi never got the sands of time because there was no older Omi. His blunder caused him to land in a world where Jack Spicer rules.

[Tobias]

Gargoyles: Goliath only choosing to take Hudson with him in part 1 of 'Awakening'. Even if he was still doing what would be in the best interest of the clan without realizing he'd been betrayed by his true love, his mistake in only taking one other Gargoyle along with him resulted in most of the clan (with the exception of the trio, Bronx, and Demona) getting slaughered.

[Collie]

Everybody who finds some ancient talisman or map that can unleash a force of incredible power, and then doesn't destroy said talisman or map. Most recent example I can think of: The Secret Saturdays and the Kur Stone. The stone is a map to the tomb of a being capable of conquering the world, but he won't wake up unless someone wakes him. So, reduce it to dust and there's no problem!

[STARTOUNZ]

At the end of The Spectacular Spider-Man episode "Intervention", Spidey tries to destroy the alien symbiote by putting it in a freezing chamber. Having a scientific background, Peter should have easily known that wouldn't work since it's survived the cold vacuum of space. This, of course, leads to the symbiote bonding with Eddie Brock, becoming the vengeful Venom. And he would have had his revenge for sure it the symbiote wasn't stupid enough to be tricked by Spidey, claming he wanted to bond with it again. It should have sensed his deceit and not separate from Eddie. It's surprising Peter never used its true weakness of sound against it. Surely, that would have been the better option.

[Cartoon X]

In DBZ Vegeta allowed Cell to reach perfect form, letting his pride endanger the entire universe. Gohan also made the mistake of toying with Cell to make him suffer, instead of right off finishing him.

[defunctzombie]

Chihiro gasping at the frog would be a big one in Spirited Away. None of the other stuff on the bridge was weirder than a talking frog? :anime:

[Lighthammer]

There's a bunch, but I'd need to sit down and think about this one.

One I recently watched was in Captain N: "Videolympics".

The N Team seriously thought Motherbrain was magically going to give up if her rag tag team of misfits beat the N Team.

Seriously ...

[Silverstar]

The Z Soldiers, after receiving the warning from Future Trunks about the impending invasion of the Androids in 2 years time, stupidly opt to train for those 2 years so they'll be ready when the Androids come, instead of going along with Bulma's decision to take out Dr. Gero before he ever gets the chance to invent the Androids. Is flexing your muscles really so important that you have to put the entire planet in danger just to show how hard you are?

[A.Magik]

I have a tricky one. It comes from the first Fullmetal Alchemist Anime...

Spoiler:

Roy Mustang's revenge on Pride/Fuhrer Bradley. We learn of Roy's promise to Hughes that he follow the right path to be a great man (meaning no revenge, in a scene where Edward is all for it). However, what does Roy do? He avenges his best friend's death by killing Bradley for revenge! He succeeds in his plan, but at the cost of an innocent child's life. Evidently, Selim Bradley's devotion to his father was something Roy didn't consider in his plan. The guy definitely had too much 'grief=rage=revenge' on the brain (and this is not some Anime1 OOC nonsense: the manga's Roy was also too easily drawn to revenge against the murderer of his friend).
However, playing Devil's advocate, What choice did Roy have? His earlier ambition of rising up the ranks was now a pipe dream. The list of allies with enough power to take down a Homunculus was thin: Izumi was coughing up blood. Armstrong had to protect Roy's besieged subordinates. Edward had to deal with rescuing his brother from Dante. So Bradley was Roy's job. Besides, the clock was ticking on the invasion of Drachma, which Bradley assigned Roy to commence. Now that he knew the reasons for the wars, Roy could not let another Ishbal Massacre take place.
So what we have here is a 'darned if you do/darned if you don't' situation. Bradley had to go, and his destruction ended the Homunculus' control on the country. However, with the effort Roy put in trying to redeem himself for past deeds, to end up committing selfish revenge- and to have that path lead to a child's death- must have been a heavy blow to the man (hence his situation in Shamballa). One more mistake he will always regret, for all the good it did.

[Lavenderpaw]

Jake Long from American Dragon, though he always redeemed himself he was the cause of a lot of his own problems.

[judyindisguise]

1. Simba trusting his uncle Scar
2. Tarzan trusting the human explorers (which cost his "father" his life. One of the reasons I've never warmed up to Disney's version of the Ape Man).
3. Wanda marrying Cosmo
4. Tinkerbell falling for Captain Hook's false sympathy
5. Aladdin not freeing the Genie the first time around

[Tobias]

5. Aladdin not freeing the Genie the first time around

That would have made for a very downer ending since Jafar would have ended up killing everyone since he would have still been roaming around free.

[blazecat]

1. Krillin not pressing the remote that would have shut down Android 18 (thus preventing Cell from absorbing her).

2. Terra betraying the Teen Titans and secretly working for Slade.

3. Otis the cow partying while his father (Ben) was defending the hen house against coyotes (he died while trying to protect it).

[TheGunheart]

There's this obscure French cartoon called Jason and the Heroes of Mount Olympus that I swear was the king of this kind of thing.

See, the three main characters all had super powers. Hermes could fly fast enough the cause tornados if he flew in a cricle, Aphrodite could control plants, and Jason had a belt that essentially could do whatever the plot needed.

As you might guess, they NEVER use these powers when it could actually be useful. One episode we could have Jason throwing rocks at skeletons, and a couple later he uses his belt to summon a full set of golden armor and a sword.

[tucsoncoyote]

This goes back to Collie's statement about a powerful artifact that should be destroyed and not split up or used by said protaginists. After all this one involves of all things, time travel and the paradoxes that are created when an item is destroyed in the future as the future hasn't even happened yet.

For this example, Kim Possible not stopping Dr. Drakken, Shego, Duff Killagan, and Monkey Fist from stealing the Body (And later the head) of the Tempus Simia Monkey in A Sitch in Time. With the villains in control of a very powerful artifact that can open time portals, the villains go back in time to break up Kim and Ron's friendship in Pre-K, then try to stop Kim from going on her first mission as a pre-teen. It's only then that Shego uses the Time Monkey and takes over the world some 16 years into Kim and Ron's present.
Only by later destroying the time monkey does the entire take over the world plot fails..but then this brings up a paradox as the idol is not destroyed in the present (2004), but rather in the future (2020), which means the ramifications of a time loop begin because the idol exists in the past(1993) and present(2004) but not in the future (2020). Had Kim and Ron used the idol to go back to the present and destroy i at that point, initally before the villains had accquired it, then the events of what happen 16 years into the future would not exist. So in the end Shego will take over the world in about 14 years in 2020 as the idol does exist.. until Kim destroys it, which will cause a time backlash and Kim and Ron go back to 2004 and live the 16 years of happiness over and over again ad nasuem.

But then we have another paradox. What would have happened if teenage Kim (who is 16 or 17 at the time), had destroyed the idol in the past when she was just 4 years of age? Then you have the ultimate paradox as either 4 year old Kim would suddenly become 16 or 16 year old Kim would not exist as you can't have one person who is two different ages (One of the two would exist, the other would not) who's best friend is a 4 year old boy. but the friendship would last but there would be an age difference of some 12 years or that the events of Ron Moving away would occur. So while Ron is 16, Kim would be 28 and thus dating Ron would be out of the question. or the events of the Alien Invasion in Graduation would occur and Kim would die at the hands of the Lowardians without Ron ever having to save her. so Kim would die at 18, and Shego would still take over the world in 2020 using a means to defeat the Lowardians and be considered supreme ruler.

Either way, Shego wins.

Way to go princess..