Nominating Ogerpon-Cornerstone to B+
Based off of the work that her sister, wellspring, puts in, a lot of people might think that the opportunity cost for using Cornerpon is probably not worth it.
However, cornerpon is actually a bit better in some regards and definitely a great mom if you need it to fill other specific niches.
A glaring weakness one may bring up is that basically any steel walls it's stab combo, however, all steels in the OU tier besides Crown, Ghold, and Kingambit are hit neutrally by one of its stabs. You can also fit in either knock or superpower to let it hit it's checks.
There's actually not a single OU mon besides ghold/Kingambit (depending on which you would rather hit)
That resists both the stab combinations + the coverage (you can consider Zama a check ofc but it's... Zama.)
This makes it a crazy wallbreaker, since alot of checks for wellspring actually lose to cornerstone, which means it can break fatter teams alot more consistently, along with threaten stall alot more (since most stall run woger checks. There's not that many consistent cornerpon checks)
Finally, if you manage to keep hazards off the field, sturdy can actually be really helpful for a free turn to setup or to just guarantee a kill on something faster.
Imo it's not as good as wellspring because her typing is honestly better defensively, and water cudgle is honestly more spammable. Utility sets on woger are better, and it can also afford to run encore or other utility moves on some sets while corner running it is kinda iffy.
However cornerpon definitely has her niche.