Goku has consistently remained at the center of the Dragon Ball franchise as the mightiest hero in the world, but no one is ever going to mistake his brains for being bigger than his brawn. He's not quite dumb by any means, but his nativity has caused Goku trouble more often than any planet invading baddie.
Despite being the most pure-hearted character among the cast, Goku has made some decisions that weren't too bright and were fatal enough to put the entire universe in danger as badly as any other villain. On a smaller scale, some of Goku's actions directly led to his own deepest traumas.
10 When He Killed His Grandpa
As a child, Goku, while raised by his Grandpa Gohan, turned into a Great Ape and accidentally killed his caretaker. He obviously did not mean to do this as he had no control over his actions once transformed, but in killing his grandfather, it forced Goku to essentially raise himself alone in the woods for years until he met Bulma.
That middle period had to be an incredibly difficult period for Goku that was brought on entirely by his own actions, whether inadvertent or not.
9 When He Spared Piccolo
Demon King Piccolo emerged in Dragon Ball as the fiercest foe that Goku had met in the franchise at that point and the franchise's most dangerous villain yet. Years later, it appeared he returned even worse reincarnated as Piccolo Jr., who Goku just barely beat by the skin of his teeth.
Despite knowing how dangerous he could be, he not only stopped Kami from killing Piccolo but gave the villain a Senzu Bean. Sure, Goku knew that Piccolo dying meant no more Dragon Balls, but if the Guardian of the Earth was okay with sacrificing the artifacts to vanquish a monster, so should've Goku. He's just lucky that Piccolo decided to join his side later in life.
8 When He Forgave His Brother
Goku's naivety has been brought up a few times during this list. It's actually always been a key aspect of his character even prior to the start of Dragon Ball Z, but he certainly does not waste time to showcase it at the very beginning of the Saiyan Saga.
Despite barely knowing this man who claims he's his brother and after this same man dedicated his first five minutes on earth to kidnapping Goku's son, the World Tournament winner was compelled to believe Raditz's pleas for surrender, only to be blindsided. If he didn't let go of Raditz's tail so easily, maybe Goku wouldn't need to put himself in a position to be killed; Piccolo could have just shot Raditz while he was prone on the ground still.
7 When He Spared Vegeta
As powerful as both Piccolo and Piccolo Jr. turned out to be, Vegeta was even stronger, nearly killing Goku if not for some background assistance from Gohan, Krillin, and Yajirobe. Perhaps because he had the foresight and a killer instinct that Goku failed to ever have, Krillin was ready to kill Vegeta on his way back to his ship.
Goku stopped him simply on the off-chance that they could meet again and fight one day. Vegeta coming to earth led to more than half of Goku's friends dying, but he was willing to risk the fate of the galaxy all over again just to fight again.
6 When He Gave Frieza His Energy
Goku giving Frieza his energy has always been a big talking point among the Dragon Ball community when discussing their fight on Namek, but truthfully, that is merely the tip of the iceberg. First, he merely walks away from Frieza to end their fight telling Frieza to "never do mischief again," turning his back as if that'll be enough for Frieza to think twice about his evil ways.
It isn't, and so he sends death saucers after Goku. When that backfires, that's when Goku gives a chopped up Frieza some of his energy to survive. Turning his back again nearly gets him killed when Frieza uses that energy to fire one final ki blast.
5 His Cries Unearthed A Legendary Super Saiyan
Maybe this one should not count because the original Broly trilogy isn't even canon anymore (it's debatable that it ever was, to begin with), but nonetheless, there was once a time where Goku singlehandedly created one of the biggest thorns in the Z-Fighters' sides just by crying.
Sure, being annoyed by a crying baby is a weird backstory for the Legendary Super Saiyan to activate his powers, but that does not change the fact that arguably the strongest villain who Goku ever faced across a trilogy of movies was created solely because he cried too loud next to Broly's crib.
4 When He Forfeited The Cell Games
When the Cell Games commenced, despite the fact that the fate of the world was on the line, Goku almost immediately gave up when he forfeited a brief bout with Cell. Under the impression he didn't have what it took to beat Cell, Goku sent his 11-year old son into battle for him believing Gohan could destroy him.
Sure, Goku's instincts proved right, but he didn't make his son's job any easier by giving Cell a Senzu Bean for a "fair" fight. Maybe if he didn't give Cell that extra boost, the fight would've ended sooner and Goku wouldn't need to sacrifice his own life. Even worse, he forced his son into some deep trauma just to help Gohan unlock his full potential.
3 Giving Majin Buu The Energy He Needed To Return
To Goku's credit, this one was not entirely his fault. If anything, it's Vegeta's fault. Still holding a grudge for being beaten and outclassed by a lower classed Saiyan, Vegeta allowed Babidi to turn him into a Majin so that he could goad Goku into another fight without remorse.
Goku fully understood that a fight with Vegeta would provide enough energy for Majin Buu to be revived - and it does - but it was either fight Vegeta or let Vegeta kill pedestrians at random. Without better options, Goku made the right choice, but nonetheless, every evil thing that the pink monster does during the Buu Saga is a direct result of Goku agreeing to fight Vegeta.
2 Bringing Frieza Back To Life
When Majin Buu was out of the Tournament of Power, Frieza was in representing Universe 7 under the condition that if they win, then Goku must allow for Frieza to be brought back among the living permanently. Goku agreed and against better judgment, stood on his promise by granting Frieza his wish.
While being a man of his word is admirable, but not at the expense of knowing the damage that Frieza could do in the future, given his pedigree. And given what he did in the Broly movie almost immediately after the Tournament of Power arc, it's safe to say he's setting up to do much, much worse in the future.
1 Kickstarting The Tournament Of Power
If Goku is motivated by anything throughout the franchise, it is by becoming stronger and fighting the strongest fighters in the galaxies. This motivation got him in over his head when he convinced Zeno to craft a tournament including fighters from other universes.
In theory, it's a fun idea, until one reads the fine print indicating that the losing universe will be erased from existence. Goku put his entire universe in jeopardy just to fuel his desire to fight. Not even his most heinous enemies would take such a reckless risk.