Well, Harry might discover some hidden passageways in Voldemort's lair. Since he has a lot of experience with tricky situations at Hogwarts, he could use his wits to find a way out. Also, he could try to appeal to any shred of humanity left in Voldemort's followers, if there are any, and get them to help him escape.
In a fanfic where Voldemort kidnaps Harry, it could lead to a lot of intense situations. Harry might be used as a bait to lure his friends into a trap. Or Voldemort could try to turn Harry to the dark side, using various forms of dark magic and psychological manipulation.
He might also use his wits and knowledge of the wizarding world. For example, he could use a vanishing cabinet or a secret passageway that Bellatrix doesn't know about. Since he has spent a lot of time at Hogwarts, he may be aware of some hidden routes that could lead him to safety.
It could end with Snape realizing he was wrong. He apologizes to Harry and they form an unlikely alliance. They return to Hogwarts together and Snape has to face the consequences of his actions from Dumbledore.
Harry could also try to reason with Voldemort. He might remind Voldemort of the prophecies and how killing him might not be in Voldemort's best interest. He could also try to appeal to any bit of humanity that might still be left in Voldemort, although that's a long shot.
Often, it could end with Hermione being rescued. Maybe Harry and the others stage a big rescue mission and manage to defeat Voldemort in the process.
Anzu could use her wits. If she can find a moment when Bakura is distracted, she might be able to run away. Maybe she could create a diversion, like knocking over something noisy to draw his attention and then make a break for it.
Marinette could use her wits. If she's tied up, she might be able to find a sharp object nearby to cut the ropes. For example, if she's in a room with some old furniture, there could be a nail or a broken piece of wood that she can use.
Well, Bumblebee could try to escape by building a device from the scraps he finds in Megatron's place. He's a resourceful Autobot. He might be able to create a communication device to call for help or a weapon to fight his way out. He could also look for any weaknesses in Megatron's security. Maybe there's a power source that, if disrupted, would open all the doors. Bumblebee could also try to form an alliance with some of the other captives or minions in Megatron's lair who might be disgruntled and want to escape as well.
Ezra could use his connection to the Force to manipulate the environment around him. For example, he could cause distractions by making objects move and then slip away while the Inquisitor is distracted.
In the fanfic, Harry might reach out to Voldemort to save him because he believes that every life is worth saving. He uses his connection to Voldemort through the scar to communicate. Harry shares memories of love and friendship with Voldemort, hoping to awaken some long - lost humanity in him. As a result, Voldemort begins to have doubts about his quest for power and domination, and a strange alliance forms between them as they face the challenges that led Voldemort down the dark path in the first place.