• Crouch, Dash, Run: All three of these actions have 10% Heavy Armor (in other words, if Bowser is Running, Dashing, or Crouching, you need to do at least 11 damage to bust him out of his armor).
• Fsmash: While being charged, Fsmash has full super armor and has a weak windbox that will drag careless opponents into where bowser is standing. The move overall does way more shield damage and has increased knockback, as well as super armor upon release until after the hitbox comes out. If charged completely, the move is completely unblockable. During charge, starting at frame 15, bowser can tap the control stick forwards or backwards to do an FADC.
• FADC forward (Tap forward on control stick during Fsmash charge): Bowser leaps forward. Invincible until frame 27. On frame 15, can be canceled into grab. On frame 27, can be canceled into shield.
• FADC backwards (Tab backwards on control stick during Fsmash charge): Bowser skuttles backward. Invincible until frame 19.
• Usmash: Has an extremely large tripbox that does 0 damage, comes out when bowser hits the ground, and causes opponents in a fairly large radius to trip.
• Dsmash: considerably faster in both startup and execution; harder to SDI out of.
• Uthrow: Serves as a launcher
• Fthrow: Serves as a kill throw, in a pinch
• Dthrow: Should be your go-to throw. Dthrow hits the opponent down in front of bowser with an angle that forces them to tech. This can lead into a nasty tech chase. Oh, and it does a ton of damage.
• Grab: Invincible startup. Pressing B within the first 4 frames causes it to cancel into a pivot grab (this allows you to pivot grab literally anywhere you could normally grab).
• Dash attack: Important. Sends Bowser shooting across the stage with full super Armor (with reach akin to E. Honda's Headbutt), launches the opponent in a way that allows for follow-ups.
• Fair: A slight flame disjoint added. Does more damage, has better knockback.
• Nair: Has IASA about halfway through the move.
• Uair: has 15% heavy armor through most of the move, has considerably better knockback (with fire!).
• Dair: Important. has 10% heavy armor from shortly after startup to near the end/when it lands, does a lot of damage, and the landing hitbox launches the opponent for another combo (or a sideB techchase).
• Bair: An absurdly strong semi-spike, Bair will score ridiculous gimp kills, and do so very safely, because Bowser's Shell is completely invincible. You know, the part you're hitting your opponent with. This makes the move absurdly hard to beat, and trading with it means that your opponent is dead offstage. Onstage, it can be used as a relatively risky approach, but the landing animation has a hitbox that will often shield poke and protect you... sometimes.
• Firebreath (B): Super armor starting on frame 5 and ending when the fire starts coming out. Hold A during startup to cancel into Running Bear Grab.
• Running Bear Grab (B + A on the ground): Bowser starts running across the stage with full super armor. If an opponent comes within his reach, Bowser grabs him with an alternate grab, leading into:
• ==> Flying Slam (B + A => Forward Throw): The SideB Flying Slam. Not very useful, compared to the other options.
• ==> Shell Crush (B + A => Back Throw): Bowser rolls over the opponent, then flings them backwards. This move does a good amount of damage, and has a ridiculously low angle. If your back is to the ledge, this will kill very, very early.
• ==> Piledriver Slam (B + A => Up Throw): Bowser grabs the opponent, jumps high in the air, and slams him against the ground. A very solid vertical killer, and does EXTREME damage.
• ==> Discus Toss (B + A => Down Throw): Probably RBG's best throw. Bowser swings the opponent around and slams them to the ground. This move forces a tech chase. And here's the thing: bowser is really, REALLY good at tech chases in his current form, because SideB can cancel into the Discus Toss as well.
• SideB (grounded): Flying Slam is still decent as is, but the real trick is, if you hold the A button once you hit the opponent, the throw cancels into Discus Toss. This is incredibly useful for keeping the tech chase going, and remember – Discus Toss does 18% each time you land it.
• SideB (Aerial): Hold the A button during the Flying Slam to cancel it into the Super Pile Driver. It's currently kinda glitched (doesn't do what it's supposed to do), but that's getting patched. It should do considerable damage and bury the opponent in the ground.
• DownB (Grounded): Can be canceled during the starting hop into aerials or a jump.
• DownB (Grounded or Aerial): While Bowser is falling, hold the B button to slow down the fall. This does less damage, and if you hit the ground while holding the B button, you incur less lag. This also allows for a trick where you press the B button just before hitting the ground to halve your lag.
• UpB (Aerial): Bowser recovers instantly from his specialfall upon landing.
• Slam Stunna (Final Smash): Bowser roars at the area in front of him, causing anyone within a fairly wide radius to immediately land on the ground and be stunned, taking heavy damage. Immediately afterwards, Bowser grabs any opponent hit by the roar and executes the Piledriver Slam throw. This will be a OHKO most of the time if it connects.
  

This matchup is a testament to just how crucial Bowser's weight class is. MK's options are so much better, Dsmash just wrecks bowser's shit, and the fact that Tornado cleanly beats Dair (I honestly have no idea why!) makes getting out of the air from above something of a chore. Additionally, although this should get patched out soon, Bowser's Discus Toss tech chase does not work the way it should against MK; he simply hits the ground and can tech immediately, instead of bouncing and then needing to tech. Shuttle Loop can kill Bowser ridiculously early, as can Glide Attack, due to its amazing angle. So... why is this matchup pretty even? Well, because MK has to land a bunch of hits, and Bowser has to land like three. MK will die to a wild Bair or Fthrow near the ledge under 70% almost all the time. MK's strings and followups are at least somewhat stuffed by Bowser's great defensive options.
Things to watch for:
– Random shuttle loops. If MK is comboing you above him and you are near the ledge, DI up. You absolutely have to be ready to DI shuttle loops, because the base knockback on that move means that Bowser can and will die about 70% earlier than he ought to.
– Tornado beats dair. Every time. Falling dair and associated mixups can still be useful, sure, but throwing out a wild Dair within reaction will get you wrecked.
– Do NOT try to DI dsmash down and tech. Every time you do this, the MK gets another free run-in Dsmash. DI up, then just try to land onstage somehow.
– If the MK whiffs an upB at you, you generally have some pretty potent punishes. Bair, if you are facing the right way, covers a lot of stuff, but the really important thing is that you avoid the glide attack follow-up, because that shit is deadly.
– Try to avoid blocking. MK's shit is really good on block. Instead, look into where your next armor fix is coming from, and try to block his shit that way.
– Feel free to follow MK offstage, just don't overextend yourself (think of what a smart marth player would do off the ledge against a recovering metaknight with his bair, and that should give you an idea). Your air movement is generally better than his, and both fair and bair can score some stupidly early kills offstage and are pretty shape. Just make sure that whatever you do, he doesn't end up between you and the stage horizontally or between you and the lip vertically, as that is gonna be a stock loss a lot of the time.
– If your opponent is overly aggressive (most Brawl- MKs are going to be used to playing VERY aggressively), start throwing out RBG at opportune moments. The idea is to make the MK second-guess themself, and nothing does that quite like dying at 70% because someone armored through your pokes.

Samus is so great in Brawl- primarily because her zoning game is so good. It's hard to get around the homing missiles, and if you try to reflect them, you'll generally eat a zair. Bowser doesn't have to deal with that shit at all. Dash attack tears straight through them, leaving her only option the Super Missiles (which clash with dash attack). That's not a position Samus wants to be in. Additionally, she also has no truly great options against approaches from above, because despite her amazing anti-air usmash, upB, and uair, Bowser's dair stuffs basically everything.
Things to watch for:
– If you aren't careless with her charge shot and avoid her (pathetic) smash range, you will not die until the range where Super Missiles start killing. That range is approximately 200%. She should start dying around 120%. That's disgusting.
– Don't get caught offstage. Ever. If you're in a fair string, finish it and then high-tail it back to the ledge, because spikes will fuck you up and missiles make landing a dair spike against an offstage bowser way too easy.
– Running Bear Grab loses to her standing, running, and pivot grab every time. Be really careful about it.
– If there isn't a super missile on the screen and you're not the entire length of the stage away, just dash in and do stuff (Dash attack is the most reliable option, but if you're feeling risky, you can mix it up). The running armor beats a lot of crap.
– Mix up your dair approaches carefully. Don't start the move unless you're already really close to the ground, because guessing wrong and eating spotdodge -> uair -> combo is just not fun.