Given his pure-hearted nature and gullibility, it's only a given that Goku has made his fair share of terrible decisions across the series. The worst of the bunch are mentioned below, although Goku has never let these mistakes wear him down in the slightest, which is pretty admirable indeed.
The first antagonist of Dragon Ball Z was also one of the most imposing of the lot. Raditz was Goku's brother and tried his hardest to bring his brother back, even going so far as to kidnap his only son.
While Goku and Piccolo gave Raditz a run for their money, the enemy had the upper hand for the most part... that is, until Goku managed to grab Raditz' tail. However, Goku's brother managed to dupe him with some empty words before landing a sucker punch and forcing Goku to sacrifice his own life to defeat Raditz.
The journey through Snake Way made for one of the longest boring stretches of episodes in the entire series. The anime made Goku look even more incompetent here by adding a bunch of fillers that made his journey even longer.
From getting stuck in a palace to falling off Snake Way — Goku definitely wasted a ton of time during this journey. Given how urgent the threats of the other two Saiyans were, it goes without saying that Goku should've been more focused while traversing Snake Way.
Before Goku could make his way back to Earth, the Z Warriors had to keep the Saiyans occupied until then. Suffice to say, the results were absolutely disastrous.
Yamcha was blown up by a Saibaman, both Tien and Chiaotzu gave their lives to protect Nappa, and Piccolo sacrificed himself so that Gohan would live. If Goku was early, then at least some — if not all — of these fighters could've stayed alive.
Goku's fight against Vegeta makes for one of the most legendary battles in shonen history. Beating the Prince of all Saiyans was important to save Earth from wanton destruction and prevent this diabolical figure from attaining immortality.
A critical point in the fight came when Goku had to hit Vegeta with the Spirit Bomb. However, before he could unleash its power, he was caught off-guard by Vegeta and lost half the energy he accumulated, making the fight even more complicated.
A common problem that most people associate with Goku is his lack of responsibility as a father. He wasn't around for most of Gohan's childhood and didn't really understand his kid either.
Even though Gohan preferred peace to battle, Goku just assumed that the thirst for battle that was so prevalent within himself would be there in his son as well. This led to Goku being hard on Gohan in training — something that was especially evident while they were training in the Hyperbolic Time Chamber during the Cell Saga.
During the Cell Games, Goku had the brilliant idea of throwing his son to the wolves to make him unleash his true potential. This was already bad enough as is, but Goku made things even worse.
He gave Cell a Senzu Bean, so he could fight Gohan at full strength, pummeling the kid around over and over again. It took a few choice words from Piccolo to make Goku understand the mistakes he was making.
After his noble sacrifice, Goku was given a free pass to roam around Earth for a few days. This was around the same time when the Martial Arts Tournament was being held and Majin Buu was released after Goku and Majin Vegeta's battle.
During a particular moment when Goku wanted to buy some time for Trunks, he decided to reveal a new transformation during his battle against Majin Buu. It was an epic moment... but it also depleted most of the time Goku had to roam Earth.
After attaining the power of a Super Saiyan God, Goku fell back on his training once again. Only later did he realize that Vegeta had gone behind his back and was training with both Whis and Beerus.
In the grand scheme of things, this wasn't really a problem. After all, Vegeta hadn't received the boost of power attained from becoming Super Saiyan God, and used this time in training to catch up to Goku's power level.
The tournament between Universe 6 and 7 was pretty fun, featuring many great battles and transformations. Seeing the universal counterparts of fighters everyone knew and loved was quite novel indeed, with Frost being a great example of the same.
While he seemed like a stand-up being, it turned out that Frost was a cheater who poisoned both Goku and Piccolo. The former didn't even realize why he lost, with Jaco revealing Frost's deception for everyone to see.
Watching Goku unlock Ultra Instinct was one of the best moments in the entire series. He used an imperfect version of Ultra Instinct in various fights before unlocking the Mastered version during the ultimate fight against Jiren.
The battle was absolutely brilliant, although Goku ended up wasting the limited time he had in this form. As a result, his body couldn't handle the pressure of Ultra Instinct and reverted back to his base form, which made the final stretch of the fight way more complicated than it should've been.