Alex has been sailing on his lonesome for quite a while now. He didn't want to risk his comrades' lives only for this silly mission, so he would have to do this one on his own.
He had thought about how high his chances were. On one hand, he believed himself capable of taking on the majority of the Whitebeard pirates; on the other hand, there's Whitebeard.
Nothing else to say, Whitebeard was a symbol of strength and widely regarded as one of if not the strongest man in the world, except for monsters like Xebec, his captain, and maybe Roger would be above him as well.
Basically he was fucked, and he knew it, so he didn't waste his time just sailing in some small ship; he lost his ship to a nasty storm, but since he didn't eat a devil fruit, he can swim.
Swimming allowed him to get into the waters of the New World and fight sea kings; along with very intense training sessions, he gained tons of experience and advanced to a stage where he would beat Wano arc Zoro in 40 out of 100 battles of pure swordsmanship.
Haki-wise, he had advanced all his Haki types to 9/10, and then his Haki hit some form of roadblock because apparently he needed combat where his life was at risk, and he knew that Whitebeard would provide such a challenge for sure.
A news coo had kindly provided him with news of Whitebeard's most recent battle and the island it took place on, so he quickly Geppo-Soru-ed his way there and searched around other islands in order to know whether or not he'd left yet; he didn't, and this was his golden opportunity: die or become a legend that survived a clash against Whitebeard.
Alex opted to dress in his Marine uniform, hiding some armor that clung to his skin and yet provided sufficient protection.
Alex wasn't honorable whatsoever when it came to facing somebody he viewed as above him; this is why Whitebeard had mere seconds to let out a titanic burst of Conqueror's Haki and a burst of his Quake Quake Fruit as Alex flashed into his crew and sliced apart the weaklings of the crew, after which he stood before his sixteen commandors and the captain himself.
"Edward Newgate and the Whitebeard Pirates, I shall bring you all to justice and deal a punishing blow to Rocks D. Xebec after I defeat you all."
Nothing else needed to be spoken as Whitebeard rushed in alongside his kids, attacking Alex with fury only a parent whose child was wounded could feel.
Alex found himself on the back foot from the get-go. He had to dodge and weave through attacks constantly, but when he found an opportunity to attack, his moves would be blocked by Whitebeard; it pissed Alex off and made him reconsider his strategy.
Jumping back, Alex decided to stop holding back and used his full Haki abilities along with drawing both of the two swords of Igris, which he received as a reward.
Marco, the pineapple-headed 1st Division commander, whistled as he sensed the immense Haki and the shift from wielding one blade to two long ones.
"Is this even real, yoi?"
Diamond Jozu, ever the confident, borderline arrogant Diamond-body guy, remarked, "Two swords and some Haki won't change shit, you trashy Marine!"
Alex smirked, and without a word, he vanished in a blur of purple surrounded by black lightning. Immediately, gashes started to appear on the commanders, and they weren't shallow either, so they started to drop to their knees, unable to fight back and actually make a difference.
"Now it's only us two, White Mustache." Alex said, egging the Pirate with a 2 billion Beli bounty on as he readied himself for the battle to come, Haki pulsing with his Heartbeat as he remembered words from a certain Flame Pillar 'Set your Heart ablaze.'
"Gulalalalalalala! Let's see whether you can put your money where your mouth is, brat."
Whitebeard charged, his Murakumogiri coated in a Quake bubble and the blade black with his powerful Haki clashing with Alex's quiet, powerful blades, pushing the youth back as Whitebeard capitalized on it and nearly knocked Alex down, putting himself in a very winning position.
Alex wasn't going to die this easily though; he simply flipped backwards using the force of Whitebeard's blow and sent out two crescent-shaped slashes at Whitebeard's unprotected chest, which were blocked with the speed befitting of a future Yonko.
Alex realized one thing: he can't win. It's not because he feared the man; he just couldn't fucking beat him. His body was a bit too weak. He could do damage with Haki, but nothing else, and he was running low on it after having fought tons of sea kings without a lick of rest.
It was a silly idea to fight right before the battle, so with that in mind, he poured all of his juice into one blade, sheathing the other as he put both hands on his sword and jumped into the air, posing like an executioner with his sword above his head, the dark and stormy weather giving him just that bit of aura needed to put even Whitebeard on guard.
You cannot defeat me, you pesky Marine. Give up and die; you can't kill someone of my caliber!"
"I have had my fill, White Mustache. Here's a little parting gift for surviving against me."
His sword glowed with purple Ryuo; armament Haki coated his sword an abyssal black as his body glowed in Conqueror's coating.
His arms trembled with exhaustion, yet he had to pull this off, or it'd be off with his head for sure.
"Answer me this, White Mustache,"
"Do you bleed?"
Alex swung down, and the world fell silent; the heavens parted in two, golden sunlight dividing the island with a line through the middle, and Whitebeard's chest was cut open, blood spurting out, but he wasn't in any serious danger of dying; that's how tough he was. He was, however, shocked into silence.
As he turned to look where this powerful Marine had gone, he found no trace of the man, gone like the wind.
"Gulalalalala, I hope we meet again, unknown Marine."