There has never been a more rebellious trio than the friends we saw on Harry Potter. Each one of the three broke rules on a frequent basis, and did so on individual terms, too. They were always spared, though, because their rule-breaking helped in denying Voldemort (or some other factor).
The greatest reason for the three never really being punished for anything (detentions aside) was Dumbledore’s favoritism toward Harry (justified, though), and this helped Ron as well. Ron was basically a scar-less and red-haired Harry, and the two were very much alike. Ron also had the same penchant for taking liberties with rules and laws, some instances being much more serious than others.
Harry was egged on into agreeing to a midnight duel with Malfoy in his first year in the Harry Potter and the Sorcerer’s Stone novel. It was largely Ron's fault. The two would sneak out at night (unwillingly bringing Neville and Hermione along as well) and were almost busted when it became clear that Malfoy had played them.
The sneaking out isn’t enough to be expelled, but planning to attack – even possibly maim – a fellow student in the dead of the night certainly is reason enough to get expelled. On top of that, it was Ron’s idea all along, so he was the brains behind the whole thing.
The Voldemort-led Ministry of Magic began a nationwide search for Harry, and Ron and Hermione were included in this too. When things weren’t so serious, Ron hatched a plan to appear gravely sick to throw off Ministry inspections, as attending Hogwarts had become mandatory by law.
After Ron abandoned Hermione and Harry during Harry Potter and the Deathly Hallows, he went to Bill’s cottage by the sea. Had he been seen here by the corrupt Ministry officials, it would’ve been an instant send-off to Azkaban for Ron. Even worse, he definitely would’ve been interrogated brutally over Harry’s whereabouts first.
Had Harry not been Albus Dumbledore’s golden boy, there would’ve been no chance he would've gotten away with flying a stolen car all the way to Hogwarts. Firstly, Ron was only twelve when he flew a freakin’ car from the city to the school, and was even seen by seven muggles doing so.
A wizard over 17 would’ve even been sent to Azkaban for exposing the wizarding world, and a Hogwarts underage student would never have been given leeway in this matter. There wouldn’t be any excuse either, since it was a boneheaded decision to fly to Hogwarts rather than waiting for Ron’s parents to come back and fix the situation.
The Ministry of Magic had it in for Harry and his friends in Harry Potter and the Order of the Phoenix, and by the book’s end, both Fudge and Umbridge had gone to incredible lengths to try to put an end to Harry. It was pure luck that Voldemort had been exposed by the time the students returned to Hogwarts, otherwise Umbridge would’ve seen to it that Ron and his friends were tried for attacking her personal goons.
Fudge would’ve extended the punishment for Harry and Hermione (when they had Centaurs abduct Umbridge) over to Ron as well, and the Minister was certainly unhinged enough to send a bunch of teenagers to Azkaban to assert dominance.
Impersonation on its own should be enough to see a student thrown out of the school, but Ron did one better (or worse in this case) by having Crabbe eat a questionable treat that knocked him out for hours.
Ron and Harry broke a major rule by infiltrating the Slytherin common room, but this paled in comparison to illegally brewing and consuming Polyjuice potion and attacking the people they were posing as. It sounds like Ron could even qualify for Azkaban, but being underage at the time would’ve saved him from prison. Being expelled, on the other hand, would’ve been an absolute certainty.
As mentioned before, the Minister had gotten too deluded to mind sending teenagers to prison, and there was no way Ron would be spared in this scenario. Fudge was convinced that Dumbledore --and Harry, by extension-- intended to overthrow him and take over the government with the student group known as Dumbledore's Army. Ron was the co-founder of this faction.
Had Dumbledore not swerved the situation by claiming the entire idea was his and the group had never officially had their first meeting, then Ron, Harry and Hermione probably would’ve been carted off to the Dementors in Azkaban. Fudge even would’ve made sure to have a huge picture of the trio in chains in the Daily Prophet.
Death was more of an issue here, but Ron seemed to be in Hermione’s mind frame by considering being expelled to be worse. The trio were certain they would face expulsion by going through the trapdoor for the Sorcerer’s stone, but accepted this by justifying that they were saving the world from Snape (or so they thought at the time).
Again, had Dumbledore not been a complete Harry fanboy, the trio would probably have been expelled, even though they did save the world from Voldemort. After all, rules are rules, and if they state that you’re not supposed to go the third floor (where a killer dog guards a trapdoor) then you’re not supposed to do that.
As before, Ron wouldn’t have escaped an Azkaban sentence had Voldemort’s return not been witnessed by Fudge himself. However, if you think the first infiltration into the Ministry wasn’t reason enough for Ron to go to jail, then his second infiltration in Harry Potter and the Deathly Hallows would 100% have been curtains for him.
Heck, he was an accomplice of Public Enemy no. 1, which meant there was no escaping an unfair trial for breaking into the government’s office.
The movie adaption of Harry Potter and the Prisoner of Azkaban only showed Harry attacking Snape in the Shrieking Shack, but the novel had all three friends incapacitating Snape at the same time. How did they even get away with this? It was Snape, after all.
Well, presumably, Snape was too excited over the prospect of having Sirius be subjected to the Dementor’s kiss to punish Ron and his friends. Plus, Dumbledore again invoked his it’s-Harry-so-it’s-okay rule, which got all the friends off scott-free. Hogwarts sure is a weird place, with kids being allowed to attack teachers at will and then head off for dinner in the Great Hall like it’s an everyday thing.
All right then, we’ve saved the most significant for last, since this action would’ve caused Ron to not only be wanted by the Wizards, but by the Goblin race as well. Gringotts was like a sacred stronghold, breaking in seemed to be like committing the most unspeakable of crimes, and Ron... welll, you know what happened.
Along with his friends, Ron used the Polyjuice potion, the Imperius Curse (an Unforgivable curse, mind you), assaulted Goblins – and the biggest kicker of it all was releasing an actual dragon into the world. We don’t know what that dragon did, and it may have munched on some poor unsuspecting humans after its flight to freedom. Every death or destruction caused by that dragon is on Ron and his friends. So, it’s off to Azkaban for you, Won-Won.