Now, I nominate Skymin to stay banned, seeing as there's conversation about unbanning it for Grass. As a Grass-User, I try to not see this in a Grass User's perspectives, and when I look at it this way, I see that Skymin is a monster...
LITERALLY NOTHING in this Metagame will appreciate switching into a Seed Flare, risk getting their Special Defense dropped, and then their check is
dead, and you begin to laugh as your opponent flinches your entire team to death... not a good feeling right? Now, lets see what things Skymin can manhandle for Grass,,,,
VS Fighting
This isn't even worth posting calcs, honestly... Scarf Skymin sweeps Fighting Mono, simple.
VS Ice
252 SpA Shaymin-S Air Slash vs. 252 HP / 0 SpD Abomasnow: 266-314 (69.2 - 81.7%) -- guaranteed 2HKO
252 SpA Shaymin-S Air Slash vs. 248 HP / 0 SpD Avalugg: 213-252 (54.1 - 64.1%) -- guaranteed 2HKO after Leftovers recovery
252 SpA Shaymin-S Air Slash vs. 0 HP / 4 SpD Rotom-F: 54-65 (22.4 - 26.9%) -- 38.2% chance to 4HKO
252 SpA Rotom-F Blizzard vs. 0 HP / 4 SpD Shaymin-S: 780-924 (228.7 - 270.9%) -- guaranteed OHKO
252 SpA Shaymin-S Air Slash vs. 0 HP / 0- SpD Mamoswine: 195-231 (54.3 - 64.3%) -- guaranteed 2HKO
252+ Atk Life Orb Mamoswine Ice Shard vs. 0 HP / 0 Def Shaymin-S: 437-515 (128.1 - 151%) -- guaranteed OHKO
Ice is really prepared for Skymin, but all of the checks can't continuously switch into Air Slashes after Rocks damage racks up, but if the Skymin player plays bad/doesn't keep rocks off of his side, the Ice user is in a good spot, but considering that Skymin can punch such a big hole into a team so well equipped for it... it's just outrageous.
VS Fire
252 SpA Shaymin-S Air Slash vs. 0 HP / 0 SpD Mega Charizard X: 133-157 (44.7 - 52.8%) -- 23.8% chance to 2HKO
252 SpA Shaymin-S Air Slash vs. 0 HP / 0 SpD Mega Charizard Y: 103-123 (34.6 - 41.4%) -- guaranteed 3HKO
252 SpA Shaymin-S Air Slash vs. 0 HP / 4 SpD Rotom-H: 54-65 (22.4 - 26.9%) -- 38.2% chance to 4HKO
252 SpA Rotom-H Hidden Power Ice vs. 0 HP / 4 SpD Shaymin-S: 288-340 (84.4 - 99.7%) -- guaranteed 2HKO (kek)
252 SpA Rotom-H Overheat vs. 0 HP / 4 SpD Shaymin-S: 462-546 (135.4 - 160.1%) -- guaranteed OHKO
252 SpA Shaymin-S Earth Power vs. 252 HP / 0 SpD Torkoal: 248-294 (72 - 85.4%) -- guaranteed 2HKO after Leftovers recovery
252 SpA Shaymin-S Air Slash vs. 252 HP / 0 SpD Torkoal: 156-184 (45.3 - 53.4%) -- 1.2% chance to 2HKO after Leftovers recovery
Fire is well equipped VS Skymin, but Scarf Skymin racks up so much damage with the combination of Stealth Rock+Air Slash spam, that it's going to be really hard to deal with it, since Torkoal can get Earth Powered or Air Slashed to death after Stealth Rock. Fire's match-up VS Skymin isn't really good, but it
CAN be played around, but only if the Skymin player is really dumb.
VS Flying
Honestly, Flying is so good, it's so well equipped VS every uber this banlist has to throw at it. Calcs aren't even worth posting as Zapdos/Articuno can wall Skymin, unless they switch in to a Seed Flare, get -SpDef'ed and then get bonked by an HP Rock variant... kek.
VS Poison
If the Poison user is lucky, his Nidoking or Venusaur won't get flinched, but if it flinches, the birth of HP Ice Weezing will happen.