Well, it could be that Lucius uses his powerful influence in the wizarding world. Maybe he intimidates Ron with threats related to his family's status or he uses some dark magic to create a distraction and whisk Hermione away.
In some fanfictions, Lucius might have an ulterior motive for saving Hermione. He could be using her as a pawn in a larger scheme against the Weasleys or the Order of Phoenix. So, he might save her by making Ron believe that there is some greater danger approaching if he doesn't let Hermione go. For example, he could fabricate a story about Death Eaters coming for Hermione to use in their evil plans, and Ron, being protective but also afraid of the Death Eaters, might let her go with Lucius thinking it's for her own safety.
Well, perhaps he uses his influence in the wizarding world. Maybe he has some connections or knowledge that allows him to intervene and get Hermione out of the abusive situation. For example, he could use his status among the pure - blood families to put pressure on the abusers.
Well, in some versions, Ron might use his quick wit and knowledge of Hogwarts' secret passages to outmaneuver Draco. He could lead Hermione to safety through a passage that Draco doesn't know about.
Well, it could be that Snape has been secretly observing Ron's erratic behavior towards Hermione. When the situation gets out of hand, he intervenes. He might use his position as a teacher to discipline Ron and in the process, saves Hermione. Snape is a complex character with a lot of power and knowledge, so he could use various means like his occlumency skills to sense the danger Hermione is in and act accordingly.
Hermione might become more distrustful of Ron. After being saved by Lucius from Ron, she could start to see Ron in a different light, perhaps as someone with a darker side she hadn't fully recognized before. This could make her more cautious in her interactions with him.
Another way is that Ron could call upon the help of his friends or allies. He might send a Patronus to summon other Gryffindors or even some Hogwarts professors. Together, they overpower Viktor and rescue Hermione. Ron's leadership skills and ability to rally support could be crucial in this situation.
Maybe Lucius wants to gain an advantage. He could see Hermione as a powerful witch with knowledge that he can use for his own ends. By saving her from Ron's beaten, he hopes to earn her gratitude and get access to her skills or information.
In many such fanfictions, Sirius might use his magic skills. He could be quicker and more powerful than Lucius in a duel. Maybe he uses a powerful spell to stun Lucius and then whisks Draco away to safety.
Another plot twist could be that Lucius's act of saving Hermione causes a rift between Hermione and Ron that is hard to repair. Ron might misunderstand Hermione's connection with Lucius and think she is now on the 'dark side' so to speak. This could lead to a complex love triangle situation where Hermione has to prove her loyalty to her friends while also dealing with her gratitude towards Lucius.
Well, in some fanfictions, Lucius might use his charm and power. He could be depicted as very persuasive and use his status in the wizarding world to make Hermione see him in a different light. Maybe he offers her opportunities for knowledge or power that she doesn't get with Draco.
One consequence could be that it creates a rift between Ron and Hermione. Hermione might be grateful to Lucius, which could make Ron jealous or angry. This could lead to a strain in their relationship, and they might have to work through their feelings about Lucius' interference.