Sequence breaking Metroid games — that is, the act of getting an item earlier than intended — is a time-honored tradition. In Metroid: Zero Mission, for example, it is entirely possible to get the Screw Attack, usually a late-game item, very early on by using very precise bomb jumps. Normally, players aren’t rewarded with anything except perhaps faster clear times or earlier upgrade paths, but Metroid Dread has a surprise for those willing to go the extra mile.
If you obtain the Bomb upgrade earlier than intended, you can use it to defeat Kraid’s second phase in one gruesome attack. The path to doing this is to obtain the Grapple Beam upgrade first by heading to Dairon once you’ve received the Varia Suit. In the screenshot below, there’s a room located in Dairon with a hidden block that takes you to a secret challenge room:
This challenge room requires some tricky wall-jumping, and to beat Kraid fast; you’ll need to do it in one or two shots, as your energy tanks will not be as plentiful:
After clearing this room, you will find an elevator to take you down to Artaria. Follow that path all the way to the Grapple Beam! Once obtained, backtrack to Dairon and obtain the Bombs as normal — turn the power on to the area left of the EMMI zone and acquire the Bomb upgrade.
From there, you can head to Kraid as normal. The insta-kill can only be completed in the 2nd Phase, so take out the 1st Phase as normal with your missiles. Once the second phase starts, use a Bomb to break this hidden block:
You’ll shoot out into Kraid, and from there, can hammer the Y button to drop as many Bombs as possible.