Bulk up tusk definitely is good against gambit, though it doesn't boost as much as gambit much, which is why I listed Zama as a unique counter. Encore mons definitely do screw it over a lot, but struggle does a lot funnily enough.I mean you also have counters like Zamazenta, or Bulk Up Great Tusk which hard counter any and all Gambit sets. You also straight up cannot sweep if they keep an Ogerpon in the back and you're 5 fainted, or any Encore mon in general (which includes Val).
+2 252+ Atk Supreme Overlord 5 allies fainted Kingambit Struggle vs. 4 HP / 0 Def Iron Valiant: 202-238 (69.6 - 82%) -- 50% chance to OHKO
Probably not going to happen, but it is funny.
Also, not a response to you, but to another post, but adamant gambit is absolutely something you need to account for, there is a reason why it is one of the two gambit sets used. You may be outsped by corv/skarm, but in return you have so much power and bulk.