The Chespin family is such an underappreciated and underrated starter line. It's probably the most overlooked because it doesn't have the raw appeal value of Fennekin or Froakie lines but Chespin's line is pretty great.
Chespin itself is absolutely adorable, and it's arguably the cutest of the three Kalos starters imo.
I mean look at that thing, there's just something inherently adorable about Chespin that I can't describe, but I love it so much.
The XY anime served to make Chespin even cuter imo, and Clemont's Chespin had a lot of personality and was one of the most expressive Pokemon out there. Its Japanese voice is even cuter, and absolutely sells how adorable it is, hearing it say different parts of "Harimaron" is so adorable!!!
Now for
Quilladin, I know many dislike it for how "ugly" and "fat" it looks, as people seem to think, but I think even that has its charm. It's very derpy looking and almost so silly looking and over-the-top in a way that it comes off more as ugly-cute to me: it's not very pleasant looking, but its facial expressions combined with the way it looks makes it an ironically lovable Pokemon to me.
I mean look at it. It's so derpy looking, and to some it may look pretty awkward because it's chubby, but it's got its own charm. It retains some of the cuteness of Chespin imo while mixing it in with the bulky physique and flavor of its evolution Chesnaught, who I will get into soon, and for a middle stage, this is a very good transition from adorable little Chespin to the awesome Chesnaught. I think people have some sort of negative bias against chubby looking things, which is a shame, because Quilladin really isn't such a bad design. It also kind of looks like a cocoon shell in a sense, so it's simi-metamorphic without being totally metamorphic like the bugs.
Now we get to
Chesnaught. Its 3D Model's idle pose honestly does such a huge disservice to it, but it's such an awesome and unique design in its own right. The official artworks do it more justice imho, so I'll just post those:
This is just such a neat, cool, and awesome design that is the perfect blend of tough, cool/awesome, and ironically cute in its own right as well, as you can see in the rightmost image: it's actually surprisingly cute like Chespin is. The spike shell is an awesome feature of its design, and it really looks like it's something that broke out of the outer shell of Quilladin and became a powerful beast of a Pokemon in and of itself. Between that armor and the sheer strength it exudes with its post, it looks both powerful and cool at the same time, which makes it such an awesome Pokemon in my eyes. And not to mention its in-game cry, which is really cool imo and has a lot of "oomph" to it that Delphox and Greninja's cries don't:
And not to mention, while its 3D model's idle pose is pretty meh, its attacking animations are wonderful. Look at it when it uses Spiky Shield or Protects, for example:
HOW COOL IS THAT?! Chesnaught's original signature move was Spiky Shield, which is almost as cool as Sceptile's Leaf Blade imo, but it's such a great move and Chesnaught was
built to use thihs move in such a brilliant way: it clashes its arms together and has the power to conjure up one big shield to defend itself from attacks: a spiky one no less that defends itself from any powerful blow, even a bomb can't faze it!
Its other two offensive animations aren't too bad in and of themselves and still give off a sense of power to them as well.
Chesnaught's flavor ties into RPG classes like its other fellow Kalos starters, and it fits the Fighter/Knight class of RPGs, much like how Delphox is the Mage, and Greninja is the Thief class. Chesnaught plays into this wonderfully with its design, but its stats are also beautifully executed: with 107 Attack and 122 Defense, it's a physical tank at its finest, being able to use its wonderful myriad of resistances with its amazing Grass/Fighting typing defensively, and its raw bulk combined with a divine movepool that works wonderfully with its stats: it has Bulk Up and Swords Dance (and even Belly Drum), of course, but it also has powerful physical moves at its disposal like Wood Hammer/Seed Bomb, Hammer Arm, Drain Punch, Earthquake, Stone Edge, and vice versa. And of course, it also has a wonderful support movepool, with Spikes, Leech Seed, and Roar at its disposal, as well as recovery in Synthesis. It's also unique from the other Fighting-type starters in that it's Grass-type, and not Fire-type, and its tank flavor immediately differentiates itself from Blaziken and Infernape who are faster but frailer sweepers.
Its Hidden Ability also plays wonderfully into its flavor, with it being so tough that it can withstand a bomb blast with all its armor and its shield up, and that's shown in Bulletproof, which allows it to completely block all ball and bomb based moves. Considering how common those are in competitive, this complements Chesnaught's role as a wall/tank really well and it really benefits from it to give it even more defensive utility in UU. It's a fantastic ability for it and one that works wonderfully in tandem with its stats and movepool. While it is by no means a game-breaking Pokemon, it is also not a bad Pokemon at all competitively and is still one of the more solid starters for Smogon competitive: it's no Greninja or Venusaur, sure, but its beautiful defensive/support/offensive capabilities combined have made it a solid contender in the UU metas with a niche in OU as well: it's not present in Gen 8 right now, but if it were, there's no doubt it would've be a solid contender in UU again with its ability to check/wall the likes of Krookodile, Aegislash, Diggersby, Lycanroc, you name it!
Chesnaught is also incredibly fun to use in-game in X and Y in its own right, while it may not destroy everything like Delphox or have the speed that Greninja has, and it certainly doesn't have the best matchups, it's pretty nice to have as a tanky attacker who can take hits and dish out hard in return, especially with Bulk Up or Swords Dance, and its nice movepool with strong, high powered moves in its arsenal. It's a unique and fun starter and it still feels like a starter I'd want to use and have fun using it.
Now this is not meant to be a diss at Delphox and Greninja at all: Delphox is awesome and Greninja is still one of my favorites and they are both dope as hell too. But while they have the popularity they deserve, Chesnaught unfortunately goes incredibly underappreciated but it's such a beautiful and unique design in its own right, and it's one of my favorite starters in and of itself. I think collectively speaking, while Greninja gets the most hype of them all (and rightfully so, it's awesome), the Kalos starters were really, really great and had a ton of flavor and uniqueness in design, plus their second typings and movepools make them fun and competent to use in battle in-game, plus they also comprise a Fighting/Psychic/Dark trio, which I thought was so cool back when they were revealed and still think so. They're actually up there with the Sinnoh starters as one of my favorite trios of starters and are a wonderful group of starters in their own right. But Chesnaught is just so underrated compared to Delphox and *especially* Greninja, when it's still such a wonderfully made Pokemon and so is Chespin, but I love it so much anyway.