Before you rush in to take Kraid down, you’ll need to do two things first: Get the Grappling Beam and Bombs. This is where sequence breaking comes in, since the game doesn’t really lead you to those upgrades until later on.
As noted in the description of TheSeventhForce’s video showing off this sequence break, this process can be started as soon as players obtain the Varia Suit. From there, players will take the necessary steps to get the Grapple Beam. The only tricky thing to this is a few jumps to make your way past some deadly lava pools, but a bit of patience and slick timing can get you there.
Once you’ve acquired the Grapple Beam, getting the Bomb upgrade is easy. Some well-timed wall jumps and judicious grapples will get you to the Bombs, after which you can return to where Kraid awaits.
It should be noted that the secret works only in the second half of the fight, so you’ll need to shoot at Kraid’s mouth and dodge his attacks until the fight shifts to its next phase. From there, bombing a specific spot on the wall behind Samus will launch her into Kraid’s stomach, where she can drop multiple bombs and take the villain out with very little fuss. It’s an instant kill once you use this, and players are even treated to a special cinematic for taking Kraid down this way.