Midoriya Izuku, the main character in My Hero Academia, is the embodiment of both heroics and pushing one's limits. He is a huge hero nerd who has always wanted to be All Might, his idol. Despite his greatest wish, he was born without Quirk, so he spent most of his time studying other heroes in the hopes that his knowledge would one day help him. Midoriya was chosen to be One For All's successor after his fateful encounter with All Might. Midoriya has come a long way from what he used to be, as evidenced by his fight with his classmates in Episode 23 of My Hero Academia Season 6.
One For All is an undeniably powerful Quirk, which is why its wielder can become a symbol of justice. However, it is also the reason why it is not available to everyone. All Might put Midoriya through a rigorous physical training regimen when he first received it. The young boy had to bulk up, and even then, he could only use a sliver of One For All's power without injuring himself severely. Nonetheless, this was enough for him to become one of the strongest fighters in Class 1-A – and he is now even more than that.
Midoriya is Toughened by Society's Failure
After significantly dwindling the Hero Association's forces, All For One unrelentingly continues his barrage of villainous activities. He sends out the prisoners he freed from Tartarus, allowing them to run amok. He even sends out a few assassins to take out the young Deku after granting them another Quirk. The fierce and deadly Lady Nagant is a prime example of this. It is exactly because of this that Midoriya has chosen to go solo. He doesn't want to endanger his friends and other civilians as All For One tries to hunt him down.
He's been going beyond his limits trying to take down villains and save as many innocents as he can, and he's pretty good at it. However, he can only push himself so much. Fortunately, his friends arrive just as he is on the verge of breaking down. They finish what he has started and try to convince him to step down. Midoriya, fully aware of the consequences of returning, refuses to do so, meaning the entire Class 1-A is forced to use force. They've combined their attacks to stop the rampaging Deku, all the while expressing their heartfelt emotions to him. By connecting their Quirks, they ultimately manage to catch up and capture Midoriya's heart and body.
Midoriya is Now in a Class by Himself
Midoriya's independent behaviour kills two birds with one stone. He reduces the possibility of collateral damage to All For One's manhunt by separating from his loved ones and other innocents. He also uses this time to improve his command of One For All. Not only can his body now withstand a higher percentage of One For All's power, but he has also mastered the Quirks of his predecessors. He is no longer at the same level as his peers.
The battle -- albeit without killing intent -- is proof of that. The members of Class 1-A had to combine their attacks just to stop Deku, all the while trying to talk some sense into him. While they ultimately managed to catch up to him, it's important to remember that Deku was at this point already on the verge of collapsing. If he had been even just a little rested, Class 1-A wouldn't have stood a chance.