I think ST forfeited from the competition but I feel like making a prediction anyways
Since I didn't see no one do a rematch on BB vs Magellan I'll attempt it
After defeating Bon Kurei Magellan is seen walking back into level 5, still bugged by the fact he failed to complete his duty as warden, his footsteps are slow and melancholic his rage can be seen through his expression
Magellan: How could I allow this to happen, my position as warden is compromised.
In front of his very eyes he notices a familiar figure, someone he saw earlier but did not escape in the masss breakout, this figure is none other then Marshall D. Teach
Magellan: *he speaks in a loud annoyed tone* Teach.
Teach: Zehahahahahaha. Magellan, the poison from earlier was annoying, I want to pay it back at you!
Magellan: I don't have time to talk to you, I have a job unfinished.
Just like in the first match the hydra heads appear from behind Magellan and rush towards Teach, but this time they do not make contact but instead are sucked up by Black Beard's yami yami no mi
Teach: What made you think I'd fall for the same trick? Zehahahaha you have no way of beating me.
Magellan ignore Teach's words completely and releases another 3 heads: 2 try to attack from opposite sides but teach opens his arms wide and manages to suck these 2 up like the others before but the other head using this opening strikes Black Beard directly
Teach: GAAAAAAAAHHHH!!!! *he shouts in agony of the poison that just struck him, but the poison dosen't stay long as Teach releases his darkness on himself sucking the poison out of him
Magellan: Why is the outcome of this fight different from earlier?
Teach: Zehahahahaha. Earlier you only managed to stop me, this time it's different I'll show you how fierce I truly fierce my darkness is.
Teach holds both his hands forward and they start to turn black
Magellan gets pulled straight into Teach, not expecting this Magellan is unable to react in time and gets punched into the ground by teach
Teach: Zehahahahaha! What I told you!?
Magellan punches the ground hard and releases huge amounts of Tear Gas making Teach cry cause of it and lose focus on where Magellan was
Green highly acidic poison appears from Magellan's palms in the shape of 2 normal snake heads that constrict Black Beard and burn his skin heavily making him shout in agony
Magellan: This should be enough. *He stands up and starts walking by the rest of the crew who point their weapons at him
Van Augur: Our captain is not done with you.
Magellans looks back at Teach and notices he's making a huge pillar of his darkness behind him touching the ceiling and spreading all around
Teach: Zehahahahahahahaha! Magellan! Prepare to be defeated now!
Magellan annoyed by Teach's refusal to go down starts releasing his most powerfull red poison around him
Magellan: This as gone long enough.
Both sides now posses one huge pillar of their respective element behind them towering over the burning floor 5, Magellan poison starts taking the shape of a huge skeletal demon while Teach's pillar resembles a gate of somesorts
Venom Demon: Jigoku no Shinpan
Gates of Hell...
Magellan's figure rushes into the gate that has a huge red rift crossing it from top to bottom, incapable of doing harm to it the Skeletal demon merely gets sucked in by the darkness as the rift widens and the red glow glows brighter
Magellan: This can't be!
The rift finally allows the content of the pocket dimension that the yami yami no mi posses escape and molten lava gushes out of it directly into Magellan
Magellan who posses no way to counter the molten rock completely gets defeated by the intense heat despite covering himself in poison to protect himself, the lava manages to burn trough one side of his face and leaves him with a deep scare
Teach walks away victorious leaving Magellan in the ground defeated by the intense attack