TL;DR Read the bold text/around the bold text.

Sakurai is somehow so amazing (r/smashcirclejerk) that Chrom being a canon descendant of Marth was put into Ultimate as a feature! And by that I mean that, quoting Mang0 "Chrom belongs in Melee" -- he feels like Ultimate's Melee Marth. This is due to his quick movement, combos, flow, and kill options that make a sword character great. Chrom is, potentially, the best sword character in the game in fact. What some newbies may be asking is how is he different from Roy? Isn't he an echo?

Differences from Roy

Chrom is the least echo-ey echo there is, in that he plays a lot different from Roy, as he plays more similarly to Lucina. This section of the guide isn't going to be a literal list of differences you can find on a wiki or youtube tutorial, but more applications in actual competitive play.

Nevertheless, Chrom's main difference is consistency across the sword rather than a hilt sweetspot. Now, consistency is not always better than the "peaks" given by Roy's hilt-er, it certainly is in this scenario. See, sword characters most important tools are, well their swords, who have massive disjoint hitboxes, which means swordies rely on spacing as a primary tool of attack, something which Roy lacks due to his sourspots being at the edge of his sword, severely limiting his spacing options. Chrom takes advantage of Roy's disjoints which Roy himself cannot use due to his 'special' attribute.

Essentially, Chrom is a better character because he effectively has longer reach and more consistent kill options than Roy.

Roy does have some merits and someone with a certain playstyle could definitely play Roy better than Chrom. Roy's Up-B has multiple angles and is definitely a better recovery. In addition, Roy's sourspots can be used for some kill confirms. Lastly, Roy can kill a lot earlier than Chrom due to the hilt sweetspot. Chrom, however, kills a lot more consistently, still has a multitude of kill confirms, and has one of the best moves in the game: HIS UP B.

With this in mind, Chrom's moves become a lot better in practice. For example, forward tilt becomes a much better move and an early kill option, which I'll get into more later.

Why He's Good

From a frame data perspective (all of this is true of Roy as well), Chrom has the 11th best initial dash, 4th best air speed, and is comfortably a heavyweight. With all this combined, you get a fast character who can rush you down, hit you with multiple low-lag aerials, and beat you with plenty of kill confirms.

Speaking of which, ALL HIS AERIALS HAVE LIKE NO LAG. 9 frames on Nair and 8 frames on Fair and Uair means Chrom can throw these out with little to no repercussions.

The proof is in the pudding

Ground Moves

While Chrom is excellent in the air, he is also a menace on the ground as well.

Jab, first of all, is an amazing move. It's quick and has a large hitbox. At low percents, jab can combo into his tilt attacks, and at medium percents it can combo into side B. Most of all, however, with the angle that jab sends the opponent, mixups can be done in which you can trap the opponent into a Fair, Nair, or just a run up grab. At higher percent, jab --> ftilt/FSmash can combo and potentially kill as well.

Ftilt is one of Chrom's best moves. Running Ftilt, while not the fastest, is a good approach tool that covers a lot and can even function as an anti air. Ftilt amazingly can also sometimes hit into platforms, which can net some early kills/throw opponents offstage unexpectedly. Ftilt is also one of Chrom's best ledgetrapping tools; Ftilt not only covers a large amount of recoveries, but also can hit under the ledge. Drop shield --> Ftilt is a decent option if the opponent does a get up attack or rolls behind you as well. Lastly, Ftilt is one of Chrom's main kill moves. It can kill as early as 100% at the ledge and can comfortably kill at ~120%+.

DTilt is a decent and quick move. It's main use is for either poking or for mixups on approach options. While Running Ftilt or Jab is better, Dtilt can sometimes poke shields or catch the opponent off guard.

Utilt is a combo starter and anti air. It's pretty slow (compared to his other fast af moves), and in most situations a SH UAir is a better option. However, at low percents, it can start juggles easily and can shark platforms from below.

Dash attack is very interesting. It's like a mini F-smash; it's super powerful but soo laggy. Dash attack should be used mainly as a kill option/punish if you know that this move will hit, otherwise it's not worth it. In most cases, running Ftilt is a better option.

FSmash is Chrom's best kill move and holy hell is it quick and powerful. This move can kill most of the cast at around 80%! That's insane. A legitimate option in this game is to literally dash dance or foxtrot into FSmash, as it is just that quick and hard to react to. This move should be the go-to punish or read move.

USmash and DSmash are not nearly as good as FSmash in terms of kill power, range, or quickness. They are entirely situational, with DSmash in particular being close to obsolete as there are quicker options to hit an opponent behind/below you. USmash can be used as an option after a read or to hit opponents above you on a platform.

Specials

Neutral B can is situational and is not as good as Marcina's shield breaker. The best use for Neutral B is for edgeguarding, as some opponents may fall into the giant hitbox this move has. It could potentially be used to change your momentum mid air to catch your opponent by surprise.

Side B is a good move and approach option. It can be done out of dash and can be used to mix up with your other approach options. However, it is somewhat easy to punish on a whiff or on shield. Also, opponents can sometimes DI out of the hits making it so that you're left easy to punish. Regardless, it's still a good tool to use.

As per the angles, I'd say you'd be using the "downward" angle the most, as it does the most damage and is multi hit so it can catch spot dodges/dropped shields. The "forward" angle is better for kills, and if the final hit connects it can be used as a decent kill move. The "upward" angle is not as useful as the other two and also is generally slower and laggier, but can be used as a mixup as an anti air to start juggles. Generally, use the low angle for damage and the medium angle to kill.

Counter is a decent move, it's pretty standard. It's not very spammable and is mostly good if you're expecting a powerful attack to net some quick kills. Mainly, it can be used for edgeguarding against characters who have Up Bs with hitboxes, like Mario's, Ike's, Marth's, etc.

Up B

Yes this deserves its own category; that's how vital this move is to the character. Now Up B serves two purposes: as a recovery, and as an offensive tool. Sometimes these may overlap.

In terms of recovery, Chrom's recovery is not as bad as purported to be. With Chrom's insanely high airspeed, recovering low is not that difficult and Up B can actually be moved slightly horizontally to allow for a little more control. However, his recovery is still on the bad side and can be exploited/easily deal with, especially with characters with good edgeguards like Jiggly, Inkling, Megaman, etc. However, there are some ways around this.

As an offensive option, Up B is most likely Chrom's best move. First of all, the first of the move is massive and can catch any opponent in the general vicinity in front of you. The move also has super armor on startup, in addition to doing massive damage if all hits connect, at around 23%. Lastly, the move is one of Chrom's fastest out of shield options, and can even hit opponents behind him by simply performing a turnaround-b. And ULTIMATELY, the move is an excellent kill option, being a suicide kill and actually killing the opponent first.

Now there's a section later for kill confirms, but I cannot talk about Chrom's Up B without mentioning the sacred Chrombo. The Chrombo is any combo that ends with a Up-B kill confirm. The most effective one being:

Nair --> (offstage) Fair --> (offstage) Up-B

or any variation thereof, which can include UAir. This is actually so effective that it can take stocks at 0%. Here is a vod of Zero doing the Chrombo twice in a row

Aerials

Chrom's best moves and neutral revolve around his aerials, all of which are pretty amazing (except maybe Dair, he's the black sheep of the family).

Nair is a standard Marth-like spacing tool, and is Chrom's second fastest out of shield option. Niar can be used for two things: "get away from me" or "bread and butter combo starter". Short hop Nair can easily follow up into Fair or another SH Nair, and other moves like Dair or Up B. In addition to that short hop Nair is one of Chrom's best approach options and is relatively safe on shield. Combos at low % include:

Nair --> Nair

Nair --> Nair --> USmash/FSmash

Nair --> Nair --> Fair --> Fair

From mid percent:

Nair --> Nair --> UAir --> UAir

You can get a lot more creative with the combos, especially on triplats like Battlefield where you can use the stage to your advantage. In fact, single hit Nair also has some set ups for kill confirms, like into forward tilt or forward smash which I'll touch up on later. But you get the idea.

Fair is another fantastic aerial, approach option, and combo extender. Fair, more so than Nair, is generally safe on shield as well. Fair is a great move mostly because it literally covers a large area in front of Chrom's body and can be used to cover a lot of options for opponents in front of you. Auto-cancelled Fair an be used as an approach option or just to threaten your opponent. Lastly, Fair is also a good edgeguarding tool; you don't even have to go that far out on the ledge to actually kill with it, and it covers a lot of vulnerable recoveries.

Bair is similar to Fair, except with shorter range and much higher knockback and damage. It's quick, and one of Chrom's best kill moves. RAR Bairs can be used to threaten high% opponents. It can also is one of Chrom's best edgeguarding moves, probably more so than Fair, as it can kill much earlier. Uniquely, as with all Marths, it turns Chrom around in the air, which is useful if you want to follow up with Fair or UpB.

UAir is on par with Nair and Fair as one of the best aerials in the game. Not only is UAir excellent at juggling, but falling UAir functions as a combo starter. For example, Falling UAir --> UAir. Falling UAir almost always sets up for juggles, which Chrom excels at. Furthermore, UAir is Chrom's fastest out of shield option, punishing those who attack on shield swiftly. Falling UAirs can follow up into multiple Nairs and Fairs.

Dair is situational and overall much riskier than all other aerials. Dair can be used after a hard read to spike an opponent, or to spike them on stage to continue follow ups with either Falling UAir or Nair.

Throws

Down Throw is Chrom's only relevant throw and can lead to combos at low %:

DThrow --> Up B

DThrow --> UTilt --> UAir

DThrow --> Fair -->UAir

You can take advantage of Battlefield platforms for extending combos as well. For example, after a DThrow-->Fair, you could land and FTilt or Up B.

Kill Moves and Confirms

Chrom's main kill moves are his FSmash, FTilt, Bair, USmash, and Up B. Lucky for him, a lot of his moves can combo into these moves and can kill confirm. These are listed below:

At ~80-125%: Falling UAir --> USmash

At ~60-100%: Single Hit Nair --> FSmash

At ~125%+: Single Hit Nair --> UTilt

At ~65-100%: Jab --> Bair

At ~70-115%: Back hit Uair-->Bair

Starting at 45%: Falling UAir --> (offstage) Dair

And of course, all the variations on the Chrombo starting at 0%, some of which include:

Nair --> Nair --> (offstage) Up B

Falling Uair --> (offstage) Up B

As you can see a lot of these are busted, kill really early, and are actually pretty easy to use.

Flaws

Chrom does have some flaws, of which the pros for the character greatly outweigh.

Mainly, Chrom can have trouble getting in with characters that like to spam projectiles. Working around this by rushing them down and not giving them breathing room is generally the go to strategy, but sometimes it's hard to get past a ton of shit flying at your face, especially when you're offstage and easy to gimp.

Speaking of which, and what should be obvious, his recovery isn't great. It's actually half decent, but its largely exploitable against a player who knows what they're doing.

Lastly, Chrom can have trouble hitting smaller characters as they're generally really fast in some form and duck under a lot of his aerials and slither out of a lot of his combos and confirms. A way to combat this is to perform more falling aerials rather than rising ones, or to throw out strong moves at mid-high percents, which threatens smaller and lighter characters.

Characters like Toon and Young Link, Pichu and Pikachu, and Ness, for example, may be harder to play against due to having a combination of all the tools to beat Chrom. Playing smart pays off though, and learning to beat projectile spam will help a lot.

All in All

One last thing is that most of Chrom's combos follow a basic flowchart, if you've noticed some of the combos I've listed.

Here is my cobbled together flowchart of Chrom combos

Even though this flowchart is useful, it should be like a thing in the back of your mind. Don't play memorizing exact combo combinations, just use what flows/what makes sense in the moment in the game.

All in all, Play Chrom if you like sword characters, fast characters, rushdown characters, of any combination thereof. If it weren't for the glaring weakness in his gimpability, Chrom would potentially be the best character in the game. I'm sure as the meta develops Chrom is only going to get more developed; I can only see this character as top tier unless Nintendo hits him with a nerf hammer. He really feels like a Melee Marth and it would be sad to see him be nerfed. Nevertheless, enjoy the fun that is Chrom while you still can!