Regarding starters (released and unreleased):</p><p></p><p>Venusaur: God Mon in Sun. Lots of interesting Teras, like Fire.
Charizard: Hard to use, pretty much needs Torkoal, Tusk and Hatterene (though first 2 already are 100% needed in Sun), competes with Moltres (who has defensive utility), Fire Moth, Enamorus, etc.
Blastoise: Might have a niche with Shell Smash, Specs Tera Water Water Spout in Rain or even as a Tera Dark spinner with Dark Pulse.
Meganium: My favorite starter Mon in-game for Nuzlockes. Was actually
THE BEST STARTER in GSC OU, but was literally abandoned after that. Nothing was given to it besides Aromatherapy (Dexited anyway), Overgrow (not so good on a mostly defensive Mon) and Dragon Tail (which is actually a fine move, but not enough to save Meganium from irrelevance). These are the only 3 relevant things that were given to Meganium after GSC. If Leaf Guard worked in Sun the same way as Hydration works in Rain, it could have been a fine Growth/SD + Rest sweeper, but even that hidden ability is the worst of the pack. Could have been very good with Regenerator, Natural Cure, even Triage! But no, Pokemon Company really hates this one starter. So, unless some big change happens, I don,t see future for the Grass Dino

Typhlosion: Only niche is a Sun abusser that is immune to opposing Fire Mons. Which is a fine niche, but hard to use.
Hisuian Typhlosion: This one is good due to secondary typing and Infernal Parade. Was relevant in my Wcop Final game despite me trying to throw that game several times.
Feraligatr: Tera gives this guy big potential. Enter Glowking with Chilly Reception and suddenly Tera Ice becomes a bulky DD Sweeper. Tera Dark with Crunch probably can get past Pex (not Dondozo though).
Sceptile: Has Unburden and now Tera Flying is an option. Can be a Special Attacker with several Teras too. Outclassed at everything it does, but not entirely unviable.
Blaziken: Tera breaks this guy, Ubers material.
Swampert: Rocks Pert was very bad last Gen, but there are fewer Defoggers now, so it might be good. Restalk and BandPert will be as viable as in SS, Flip Turn really helps this guy. Not very Tera dependant, which is good.
Torterra: Shell Smash goes, brrr.
Infernape: Somehow the worst Sinnoh starter but can still do some stuff with Tera. Very unexplored Mon.
Empoleon: God Mon with Roost. Not Tera dependant, just like Swampert.
Serperior: Opposite case here, totally needs Tera Blast to not be walled and even then, something always walls it. Very good Mon anyway due to high Speed, pasable bulk and Glare + Synthesis. Hidden Power removal made it worse, but Tera changing typing compensates that.
Emboar: Enormous damage with Tera, but very slow and not bulky to do it consistently. Can get past Dondozo, but needs TR or paralisis support to work.
Samurott: Competes with Meganium and Inteleon for the worst starter position.
Hisuian Samurott: Yeah, everyone knows what this guy does, its already a Top Tier Mon and I don,t see it falling.
Chesnaught: Another good Mon, the addition of Knock Off helped it a lot.
Delphox: Decent Mon, Magician does some cool tricks, versatile Tera abusser with a nice Speed.
Greninja: Another good and versatile Mon, already doing well in OU despite needing skill to be used efficiently.
Decidueye: Hard to use, there are better Mons with the same typing. However, has a trapping Move, which is always gimmick potential.
Hisuian Decidueye: Ended up being totally outclassed by every other Grass-Fight Mon. That Speed is simply too low and Gholdengo can Tera to avoid Triple Arrows and still block Defog.
Incineroar: Restalk + Intimidate + Knock Off potential. Has decent bulk and some useful moves, like Parting Shot. Can be a SD + Flame Charge + Power Trip sweeper due to Tera chaging match-ups. Hard to use, but not useless.
Primarina:
Ashirene (Primarina) (F) @ Rocky Helmet
Ability: Torrent
EVs: 248 HP / 248 Def / 12 SpD
Relaxed Nature
IVs: 0 Spe
- Rest
- Sleep Talk
- Flip Turn
- Moonblast
This girl saved my ass several times in SS OU and is common in my teams there. Checks half of the meta with the powerful typing and provides slow Flip Turn. However, Waterpon will make her life more difficult, so Specs might be better this time.
Rillaboom: Nothing to say here, already good.
Cinderace: The Mon we need to not let Gholdengo dominate the Meta.
Inteleon: Almost fully outclassed by Greninja. Needs like 6 Moves and spend Tera to be viable.
Meowscarada: Best Knock Off waifumon alongisde Weavile.
Skeledirge: Favorite Gen 9 starter, a non passive Unaware user. So good to have.
Quaquaval: Ugly duck, but pretty good at sweeping too.