Originally a non-canon character because he was not designed by Akira Toriyama, Broly was and still is the strongest Saiyan. Exiled at birth out of fear of his potential and raised for vengeance, Broly is the series strongest character who has given Goku and his friends a run for their money.
The character's popularity was so great that he had starred in three movies of the Dragon Ball Z series and the latest in the Dragon Ball Super series where he was officially made canon and introduced as a potential candidate for Goku to take under his wing in the future.
10 Born A Legend
Both Goku and Broly were born on the same day, but while Goku was born with a power level of two, which was considered an average power level the overall infants were born with, Broly was born with a power level of ten thousand and greater. This was considered very high as it already exceeded the average power level of an elite-class warrior.
So basically, Broly was born as a gifted prodigy who was already powerful enough to destroy planets whereas Goku was born with no special qualities and deemed a low-class warrior.
9 Received Only Basic Training
Unlike Goku, who has received the training and guidance from multiple masters, Kaioshin and even an angel, Broly only ever received training from his father, Paragus, on survival tactics and his own experiences while living on the planet Vampa before his father found him.
Meaning that Goku was already an exceptionally skilled fighter who had learned and mastered various fighting styles along with years of experience fighting multiple strong adversaries, whereas Broly only ever fought against Paragus during their training sessions resulting in his lack of experience in both fighting techniques and battle tactics.
8 Never Unleashed His Potential
Due to being born with an extremely high power level, Paragus developed a rational and reasonable fear of him. Broly, because of his immense strength, developed a very aggressive personality. Since his youth, his base instinct remained that of savagery so his father placed a collar around his neck which acted as a restraining device should he go, or even hint towards going, berserk.
This led to him being unable to ever truly ever immerse himself in a fight and kept his power in check so that he would never go beyond a certain amount and endanger Paragus and their surroundings.
7 Cruel Childhood
His only friend was a resident species of the planet which he grew attached to during the time he was alone. After his father arrived, his animal companion was removed from the equation, leading him to be at the mercy of his revenge-fueled abusive father who only wanted to use his strength to further his vendetta against King Vegeta for sentencing his son to death by exile.
The only memento Broly had left was the ear of his friend that was shot off by Paragus. Broly, unlike Goku, never knew love and was raised as a caged beast who would bare his fangs at his father's command.
6 Can Tap Into Oozaru State
Broly has a natural ability to tap into the Oozaru (Great Ape) state without the triggering catalyst of Blutz Waves from the moon. Like Goku, Broly does not transform into a Great Ape due to the removal of his tail but he is still able to harness the power that came with the transformation.
This allowed him to achieve new feats of strength without sacrificing speed but still makes him lose control to the savage and destructive instinct of the form. His ability to tap into the state allows him to hold his own against Goku in his Super Saiyan Blue transformation.
5 Super Fast Learner
Unlike Goku, who learned new techniques and skills under a masters' guidance for years or after the battle had ended, Broly was able to learn new ways to utilize his power by studying how the opponent fought and only by witnessing it once.
Vegeta himself notices this attribute when Broly first engages him and even considers it to be a threatening quality as it allowed him to outmaneuver and, at one point, outclass him. Broly's learning ability is incomparable to any other fighter in the Dragon Ball universe and he is easily able to learn techniques, mirroring them to near perfection.
4 Equivalent To At Least A God Of Destruction
After Frieza killed his father Paragus and unlocked his Super Saiyan transformation, Broly obtains so much power that the energy surges from his aura literally alternates from day to night. In his powered-up state, Broly is able to overpower both Vegeta and Goku in their Super Saiyan Blue form and even deliver one of the most epic and deserving beatdowns to Frieza while Goku and Vegeta regrouped.
Broly is even able to overpower Golden Frieza and fight on equals with Super Saiyan Gogeta who is multiple times stronger than both Goku and Vegeta. A ki blast from Broly could effortlessly blow up a planet equivalent or greater than the Earth.
3 Can Shatter Dimensions
During his battle with Super Saiyan Gogeta, there is a moment where both of them clash and cause the dimension to shatter. A dimension can only be shattered when two energies that are strong enough, collide with each other and break the boundaries of that frame of existence.
Meaning, that Broly alone, in his Super Saiyan state, had enough energy to overcome that boundary and it was only when Gogeta, who was equal to him at that moment, collided with him and proved that he was indeed strong enough to shatter existence. A feat that even Goku has never accomplished or come close to.
2 He Can Handle It
Goku can only maintain his powered up state for a limited amount of time and even his ace in the hole, Super Saiyan Blue with Kaioken greatly strains his body.
Broly on the other hand, can retain his powered up state for a longer period of time and it also does not strain his body as much as Goku because Goku's power is at a level where his body has adapted to the energy drain and strain but if he tries to increase it, his body starts breaking down and eventually leaves him immobilized. On the other hand, Broly's energy keeps growing and his transformation is only the first Super Saiyan transformation.
1 Survived Soul Punisher
A technique, courtesy of Gogeta, that disintegrates the enemy from the inside, the Soul Punisher or Stardust Breaker is one of the strongest attacks in Gogeta's arsenal. For Broly to be able to survive the Super Saiyan Blue enhanced version of this attack, he must have monstrous vitality, durability and ki defense which either tanked the entire blast or negated some of its more destructive capabilities due to Broly being kind-hearted.
The Soul Punisher technique is amplified if the target holds evil in his heart. The only other time this move was shown was in Gogeta's non-canon fight against evil incarnate, Janemba, who was absolutely eviscerated by the attack.