Anything faster than Gastrodon with Toxic will rain on its parade and destroy any potential it has at tanking the opposition for long. This includes Chansey, who will wall its special attacks to no end and doesn't care about status herself. Blissey, Jellicent, and Politoed are equally annoying in this respect, although if Politoed tries to Toxic Gastrodon after its STAB attack is absorbed then it most definitely won't be coming back. To use Gastrodon as effectively as possible, ensure that the opponent isn't likely to Toxic you on the switch. As a hard counter, Ferrothorn comes close if you haven't acquired any boosts with the Choice Specs set and it manages to get in safely. It's immune to Toxic, can OHKO all Gastrodon instantly with Power Whip, or can alternatively Leech Seed the switch in or just set up Spikes. Gastrodon really can't do anything to Ferrothorn unless it can hit it with a Choice Specs, Storm Drain-boosted Earth Power on the switch. Conkeldurr can also be annoying to deal with as it can boost without fear of Toxic or Scald, is not 2HKOed by any non-boosted attack on the defensive set, and can exploit Gastrodon's weaker physical defense with a powerful Drain Punch.
Gastrodon is mainly used as a defensive support Pokemon that spreads status, so any Pokemon that can absorb or block status and handily dispose or cripple Gastrodon are all good counters to consider. Grass-types are obviously the best answer to Gastrodon, as they resist both of its STAB move while effortlessly bringing down this special sponge with their super-effective STAB moves. Breloom and Celebi are particularly noteworthy counters to Gastrodon, as their abilities Poison Heal and Natural Cure, respectively, allow them to block or rinse away Gastrodon's Scald burns or Toxic poison. Ferrothorn does not appreciate Scald burns, but it will not hesitate to use Gastrodon to set up Spikes with impunity. Offensive Water-types that Gastrodon supposedly counters, can earn surprise kills on the slug with a Grass-type move. Non-choiced Politoed, Rotom-W, or Starmie with Hidden Power Grass are such examples. Gyarados, Latias, and Sub Roost Dragonite resist Gastrodon's dual STAB offense while blocking crippling status with Substitute as they set up Dragon Dance or Calm Mind. Defensive bulky Water-types can cripple Gastrodon with Toxic while having ways to avoid being afflicted by Gastrodon's status-inducing moves. For instance, Jellicent is immune to Scald burns, thanks to Water Absorb, and prevent Gastrodon's Toxic with a fast Taunt. With Hydration, Vaporeon washes away any status thrown by Gastrodon while winning the war of attrition with its own Toxic. Chansey and Blissey are also unaffected by status afflictions and special assaults by Gastrodon (except for a Surf boosted by Specs, rain, and Storm Drain), and will also wear down Gastrodon with Toxic and Seismic Toss.