First, he plays his Magnet Reverse Magic Card.  Magnet Reverse allows one to choose any Rock or Machine monster that was destroyed this turn and bring it back to the field in defense mode.  Yuugi declares Valkyrion the Magna Warrior to come back out on the defensive.  Since Yuugi summoned a monster, Osiris's second mouth activates, reducing Valkyrion's defense points by 2000, but Yuugi's Magnet Force Trap card is in play, which redirects Osiris's effect towards the God of Obelisk.  Obelisk's attack is reduced to 500 and is destroyed by Osiris's second mouth effect.  One down, two to go.

Next, Yuugi activates Valkyrion's effect to form Alpha, Beta, and Gamma, the three Magnet Warriors.  Every time Yuugi summons a new monster, Osiris is forced to strike it, and thus it sends three blasts directed at the three Warriors.  Unfortunately for Atemu, the Magnet Force trap is still in play so the first blast reduces God of Sun Dragon Ra's attack points to 1000, then the second redirected blast kills Ra for good.  The final redirected blast is enough to finish off Osiris.

That's how he did it, folks.

Aside from using that stupid title again, this is noteworthy that finally Kaiba shows a bit of humanity and realizes that Yugi is a good duelist in the dub.  Of course, the Japanese version dialogue is still better.  He originally said that now he believes Yuugi, minus the King of Games dub-only inclusion.

"Am I goin' nuts, or did Kaiba admit he was wrong?" - Joey

Yes, Joey, minus the stupid accent, you're right.  Kaiba did admit he was wrong.  The problem is, Jounouchi wasn't as surprised in the real version because Kaiba had already developed into a friend by this point in the show.  Since 4Kids trampled that, they had to add in this line.

A quick cool shot of Swift Gaia attacking Buster Blader was cut in the dub for unknown reasons.

Although there was no blood or really anything the kiddies can't look at in this shot, some white glow crap was added in the dub when Gaia pierced Buster Blader.  Nothing special here.

A little sequence of past duels with Black Knight Gaia and the Demon Summon, showing how Yuugi's monsters have served Atemu well in the past, but now they have to fight against him.  I'm assuming 4Kids cut this because they wanted the focus to be on the duel, but couldn't they have allowed a flashback amassing a mere TWELVE seconds to be shown?  I really, really don't understand 4Kids here.  Then again, no one does.  I will mail someone cash money if you can explain their logic here.

Dub-added dialogue where there was originally dead silence.  You know, 4Kids has done this since the first duel of Duelist Kingdom, and it really bugs me.  Yuugi and Atemu are having pretty much a duel to the death here, and in the dub Joey just has to cut in one last time.  Pitiful.

Cut is a point in this show where an excited Bakura lifts his fist in the air, saying that this is a close race, followed by Otogi, clearly on Yuugi's side, saying that Yuugi has two high-level monsters.  This is a blatant attempt by 4Kids at spoiling the outcome of this match by removing any mention at this point of any chance Atemu might win.  This is a clear example.  In the Japanese version it was still anyone's game, but it looks like in the dub everyone's positive Yuugi is now going to make quick work of the most experienced and powerful duelist next to Yuugi himself, Atemu.  It really ruins the drama and I wish it was kept.

This is completely mutilated in the dub and toned down to make it seem like the summoning of the Dark Magician is less of a big deal, as everyone in the dub cheering section is at this point completely convinced of Yugi's victory.