Need more discussion:
= I've earned new appreciation for P-don itself with the BU set, but aside from Gastrodon, there hasn't been much discussion about how well mono-Ground in general matches up against other gods
My own Primal Groudon team has proven reliable against literally every other God
except Darkrai, which is a goddamn nightmare to avoid being swept by. Better constructed Rain Kyogre teams, the ones carrying Ludicolo specifically, can also prove difficult to beat, but otherwise my experience with Primal Groudon is that it has a lot of matchup advantages and almost no matchup
disadvantages.
I'm particularly fond of Sturdy Leftovers Donphan. It consistently astounds me how bulky it is -I keep thinking I
must've set it to Physically Defensive, and no, it's
just that bulky- and it works as a universal check on a variety of powerful Special attackers: accept a "lethal" hit and retaliate for
actually lethal damage, or near enough and then finish them off with Ice Shard. Donphan allows me to power through the majority of "I really have no answer to this" matchup problems, and thanks to its resistance to Stealth Rock, I can even U-Turn it in -or make a gutsy prediction- and have it on full health to use Sturdy even if Stealth Rock is up. Oh, and it clears hazards too.
THINGS YOU WOULD THINK ARE A PROBLEM THAT AREN'T
Burn: Mono-Ground is very strongly Physically weighted, so Will O Wisp spam should be a nightmare, right? And Scald should be even more of a problem, because Ground is weak to Water, right? Well... no, not really. Primal Groudon can switch in on and murder almost everything that carries either, and Will O Wisp is, itself, quite rare in Gods and Followers, as Ghost Gods are unpopular and have viability problems anyway. The most common Will O Wisper is Rotom-Wash, and Pain Split is about the best thing it can to do Primal Groudon -everything Rotom-Wash usually carries is something Primal Groudon is straight-up immune to.
What few things are a problem for Primal Groudon are readily covered by Specially Defensive Storm Drain Gastrodon. It doesn't like being hit with Will O Wisp, but it doesn't
hate it, either.
Lack of clerics: You're immune to most attempts at Paralysis, and anyway you aren't expecting to win Speed wars in most cases so the Speed loss is often fairly minor. Burn is easily avoided 90% of the time, as covered above. Sleep is very rare, though admittedly Breloom is difficulty for Primal Groudon to teambuild around -but fortunately it's rare. (I use Physically Defensive Poison Heal Gliscor to deal with it) Toxic is a surprisingly minor problem, as Primal Groudon/its team tends to run aggressive enough that most of the time it won't help to drop Toxic on it or a follower.
Lack of recovery on Primal Groudon, lack of Wish: Also surprisingly minor. Primal Groudon can switch into several threats for literally no damage repeatedly, and tends to punish attempts to stay in by simply murdering whatever dared to do 30% to it. The stalliest threats are often neutered by a simple application of Rest -not even Rest
talk, just Rest. Primal Groudon's followers are also surprisingly good at keeping their own health up -my own team only has two non-Groudon members that can't restore their health.
Grass types:
Extremely rare. By far the most common viable one for me to see is Breloom on Mega Blaziken or Mega Lucario teams -both of which have consistently been somewhat underwhelming on the ladder, in my experience. It's
hard for Groudon to teambuild against strong and fast Grass attackers -nearly impossible, in fact- but most teams can't actually do anything to take advantage. I've personally taken a crack at Shaymin-Sky as a God, and it's
awful.
Ice attackers: Specially Defensive Gastrodon and Thick Fat Mamoswine both go a long way to dealing with these. Kyurem-Black is problematic, but not egregiously so.
4★ ->
3★ = I've seen surprisingly little of Aegi. Steel/Ghost seems pretty solid, but have people had any success with it? Ghost is pretty sparse as far as options go, and Steel is harder to build around than you'd think. Not sure, but I feel like 4-star is overselling it.
Ultimately I think Aegislash's biggest problem is that it isn't synergistic with its followers, or at least not anymore than its followers are synergistic with each other. Like, yeah you can switch Aegislash into a Fighting move meant for a Steel follower, but
any of your Ghosts can do that. Aegislash itself lacks recovery, has poor Wish support through Jirachi the end (Which has the problem that anything people would switch into Jirachi to hurt it probably hits Aegislash super effectively too!), and in general doesn't do anything to add value to its followers. In conjunction with Ghost and Steel both presenting difficulties for teambuilding, Aegislash tends to struggle.
3★ ->
4★ = Genesect has been doing better than I expected. I could go either way on this, as 3-star is probably fine for it, but I'd at least like to discuss the option for a raise.
Just the fact that it picks up access to a variety of useful Bugs that are either not possible to implement or, more often, aren't really worth implementing on teams that can get them (eg Mega Heracross is questionable on a Fighting team), is surprisingly useful. Genesect itself hits hard, is fast, and can U-Turn out of trouble, making it hard to actually take it down -its one of the only Gods that can be used
extremely aggressively with little risk of this leading to it being KOed.
3★ ->
2★ = We all know Mega Mom is strong, but I honestly don't see any that many reasons to use it over Arceus. Not only does it lock you out of using Mega Lop/Pidgeot, but it has generally fewer options and less sweeping potential due to 100 base Speed and non-STAB priority. I've never really seen it and I think it should drop, though it's still good enough to keep out of 1-star.
I think the main thing is:
Mega Kangaskhan is a Normal type that murders Ghosts (Crunch/Sucker Punch, backed by Parental Bond and potentially being at +2, plus Scrappy pre-Mega)
and
Mega Kangaskhan is a fast Normal type that can sweep with priority.
Problem being Arceus-Normal does the second point
better with STAB Extreme Speed, better base Speed, etc, and then Arceus can carry Mega Lopunny to do the former. So Mega Kangaskhan is basically left bringing only one thing to the table over Arceus -higher power on non-priority sweeps.
Mega Kangaskhan isn't a 1-star God, of course, because it's still Mega Kangaskhan, but it's
really hard to argue for using it over Arceus-Normal.
(Water/Steel/Poison/Fighting)
2★ ->
3★ = Not all of them, obviously, but these are some of the Arceus forms I've actually seen being used and I don't think 3-star is too much of a stretch for any of them except maybe Poison, who was probably better when Xerneas was everywhere.
I don't see Poison, personally, but I can see the others.
Genesect teams don't have a good match up against Ground and really have nothing for Don.
Genesect itself can dish out fairly good damage to Primal Groudon, and Air Balloon Heatran can force out or kill several Primal Groudon builds due to them being unable to touch it. If such a Primal Groudon lets Genesect keep U-Turning out to Heatran into Primal Groudon's face -and Primal Groudon itself is one of Primal Groudon's only good switch-ins into Genesect just carrying Iron Head, U-Turn, and Ice Beam- then Genesect can wear down Primal Groudon and open the way for something like a Volcarona Quiver Dance sweep.
I personally found Genesect one of the more problematic Gods to face as a Primal Groudon team. Not that it was a
favorable matchup for Genesect, but I had to actually make good predictions to win, rather than "Click Fire Punch until the enemy team is dead." You'd be surprised how many Dragon-using teams have nothing that can take a Fire Punch.