This is arguably the single most difficult stage in the game, though the one that follows it is not without challenging moments of its own. You'll encounter a familiar element from past titles in the series, one you might wish would just disappear for good.
Begin by charging your arm cannon as you head toward the right and use your first shot to take out a floating sentry that fires a spread shot as you approach. Past that, you'll find a tiger that is anxious to leap your way, so take care of it with a second shot. As you continue advancing, charge up shots and use them on various foes, even as you leap along a series of ledges with pits between them.
The enemies will come at you more furiously in places, and you'll often deal with two of the sentries at once, but none of them do much damage unless they manage to knock you into a pit, so you should make good progress. Eventually, you'll reach an area where a tiger is perched on a ledge. Stand on the ledge to the left and jump and fire a charged shot to eliminate the tiger. You can advance safely on either the lower or upper route from there, and climb a ladder into the next screen.
Positioned along this ceiling are some of the bulbous enemies that drop as you get near, and a spike wheel circles a platform ahead of you. After using Beat to safely eliminate the threats from afar, cross carefully with well-timed jumps. You can instead use the Rush Jet if you prefer, which is certainly safer. Then climb a ladder again.
In this next screen, there are some of the enemies that look like construction cones with small bulbs. There's also a large energy capsule that you can reach with the Rush Coil. Have Beat take out your enemies, just to be safe, then grab the energy and refill Beat's meter a bit with the special weapon capsule if needed. With that done, you can advance toward the right.
This path is guarded by relatively weak enemies that shouldn't give you much trouble. The flying red guys usually drop their explosives before they reach you, especially if you stop advancing as they enter the picture. You can also take them out with charged shots, and the same technique works even better on the additional green cones.
You'll come soon across a large bed of spikes. Use the Rush Jet to fly up to a small ledge toward the upper right, then face left and start the Rush Jet up again. Jump to it and then jump quickly off and toward the upper right to reach the top of the purple wall. Then keep advancing to the right, until you arrive at a pit you can hop into on your way to the next screen (don't miss the large energy capsule nearby, if you need it).
In the next screen, a cannon is positioned along the ground, and a cone-shaped enemy may rush you from the right, depending where you land. Take out one or both with charged shots and drop through another opening.
The next area is eerily barren at first, but as you advance toward the right, you'll come upon one of the wandering mechs that shoots lasers. Carefully aim for the jewel near its top, as usual, and hopefully it won't get in too many lucky laser shots. Past that fellow, you'll find a ladder you can ascend to what arguably are the two most difficult screens in the entire game.
Remember the disappearing blocks from previous Mega Man games? There must have been some rule saying they had to appear in each title in the series, because you'll encounter them here. Don't be afraid to wait a long while near the top of the ladder, as you watch the pattern and commit it to memory. You'll have to leap along the blocks to cross a large bed of spikes and get to a ladder near the upper left side of the screen.
In the first screen, the trick is to head along the lower blocks, follow them to the far left, then jump so that you land as the block appears not far from the base of the left ladder. It may take a bit of practice.
When you reach the top of that ladder, you'll find another room of those same wretched blocks, and another floor lined mostly with spikes. Here, though, you can cheat a bit. Watch the pattern for a bit, and you'll notice that the block which appears nearest to you lingers a long while. You can jump to it, then to a block that will appear to the upper right in due time, and then left and left again to the upper ladder. Then you should climb it to the next screen, relieved to have seen the last of the disappearing blocks in this particular installment in the series.
In the next room, there are capsules to refill energy, and a few weak enemies that you'll encounter as you advance again toward the right.
Refill as needed, and as you head toward the right, orange sentries made up mostly of eyeball will approach and circle you. Just past them, you'll find the gate that leads to the stage's boss encounter. Hopefully, you have an E-Tank or two, in case things go poorly.
When this battle begins, you find yourself on the opposite side of the screen from a green tank that rolls slowly toward you, firing occasional shots.
You should focus on hitting it with your Water Wave weapon. Ideally, you can enter the room with a charged shot ready, and release that once the battle begins. Then switch to Wave Man's weapon (don't do so until your first shot lands, though; if you pause and make a weapon switch while the shot is speeding across the screen, it'll simply vanish).
One word of advice: if your foe reaches the left side of the screen, as is likely, jump over him and then slide like mad so that you get to the right side of the screen while taking as little damage as possible. Otherwise, he'll hit you with a series of short charges that can really eat up your life meter. You want to keep some distance between yourself and your foe, so you have time to fire off a few waves. The weapon is effective and should make the fight go fairly well overall, but not if you're so busy taking damage that you can't find time to get off a few good shots.
NEXT: Stage Two